Urban Water in Japan (Urban Water Series)

Urban Water in Japan Urban Water Series ISSN 1749-0790 Series Editor: ˇ Cedo Maksimovi´c Department of Civil and En...

Author: Rutger de Graaf | Fransje Hooimeijer

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Urban Water in Japan

Urban Water Series ISSN 1749-0790

Series Editor:

ˇ Cedo Maksimovi´c Department of Civil and Environmental Engineering Imperial College London, United Kingdom Volume 11

Urban Water in Japan

Edited by

Rutger de Graaf

Section of Water Resources Faculty of Civil Engineering and Geosciences Delft University of Technology Delft, The Netherlands

Fransje Hooimeijer Department of Urban Design Faculty of Architecture Delft University of Technology Delft, The Netherlands

LONDON / LEIDEN / NEW YORK / PHILADELPHIA / SINGAPORE

Colophon Book Series Editor: Cˇedo Maksimovic´ Volume Editors: Rutger de Graaf en Fransje Hooimeijer Drawings and tables (except chapter 4) De Ontwerpers, Marjet van Hartskamp and Peggy Theeuwen, Breda Assistant: Jos Kuilboer Financial Support: Ministry of Transport, Public Works and Water Management Delft University of Technology

Cover illustration Nihonbashi Bridge,Tokyo, Fransje Hooimeijer

Taylor & Francis is an imprint of the Taylor & Francis Group, an informa business © 2008 Taylor & Francis Group, London, UK Typeset by Charon Tec Ltd (A Macmillan company), Chennai, India Printed and bound in Hungary by Uniprint International by (a member of the Giethoom Media-group), Székesfehévár. All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the publishers. Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers nor the author for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. Published by:

Taylor & Francis/Balkema P.O. Box 447, 2300 AK Leiden, The Netherlands e-mail: [email protected] www.balkema.nl, www.taylorandfrancis.co.uk, www.crcpress.com

British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data Urban water in Japan / edited by, Rutger de Graaf, Fransje Hooimeijer. p. cm. — (Urban water series, ISSN 1749-0790 ; v. 11) Includes bibliographical references and index. ISBN 978-0-415-45360-8 (hardback) — ISBN 978-0-203-88919-0 (ebook) 1. Flood control—Japan. 2. Urban runoff—Japan—Management. 3. Water resources development—Japan. 4. Municipal water supply—Japan. I. De Graaf, Rutger. II. Hooimeijer, Fransje. TC505.U73 2008 627.0952—dc22

ISBN 978-0-415-45360-8 (hardback) ISBN 978-0-20-388919-0 (e-book) Urban Water Series: ISSN 1749-0790 Volume 11

2008019324

Contents

List of figures List of tables 1

2

Introduction Frans van de VEN, Hiroaki FURUMAI and Kenichi KOGA 1.1 A Challenging task 1.2 Urbanization 1.2.1 Water resources and water use 1.2.2 The value of water 1.3 Precipitation 1.4 Drainage 1.5 Flash response of rivers 1.6 Earthquakes and tsunamis 1.7 Water quality 1.8 Concluding History of urban water in Japan Fransje HOOIMEIJER 2.1 Introduction 2.1.1 Succession of systems 2.1.2 Urban planning 2.1.3 The Tan as principle dimension for the city 2.1.4 Water as self evident element of urban space 2.2 Edo, birth of a water city 1547–1657 2.2.1 Castle cities 2.2.2 Claiming from water 2.2.3 Low-city: Shitamachi 2.2.4 Comparison with Dutch water cities 2.3 Edo, development of a water city (1657–1868) 2.3.1 Meireki Fire 2.3.2 The multifunctional water front 2.3.3 Water supply 2.3.4 The bridge as significant urban element 2.3.5 Religious places 2.3.6 Theatre, entertainment and leisure 2.3.7 Comparison with Dutch water cities

x xiv 1 2 4 7 8 8 9 10 11 13 15 17 17 17 18 19 20 21 21 23 26 26 29 29 30 30 30 32 33 34

vi

Contents

2.4

2.5

2.6

2.7

Tokyo modern water city (1868–1945) 2.4.1 Meiji 1868–1912 2.4.2 Taisho- 1912–1926 2.4.3 The 1919 City Planning Law 2.4.4 Tokyo earthquake 1923 2.4.5 Water management 2.4.6 Transformation of a water city 2.4.7 Urban space 2.4.8 Transition: pre modern industrial and modern 2.4.9 The Sho-wa (Enlightened Peace) 1926–1989: Early Sho-wa (1926–1945) 2.4.10 Comparison with Dutch water cities Tokyo the destruction of a water city (1945–1973) 2.5.1 Mid Sho-wa (1945–1973) 2.5.2 Economic focus 2.5.3 Modern Planning 2.5.4 Disappearing water city 2.5.5 Kenzo Tange’s Plan for Tokyo (1960) 2.5.6 Comparison with Dutch water cities Tokyo regeneration of a water city (1973–2007) 2.6.1 Late Sho-wa (1973–1989) and Heisei 2.6.2 1968 City Planning Law 2.6.3 Pollution diet 2.6.4 1980s 2.6.5 Liveable water fronts 2.6.6 Hachioji Minamino City 2.6.7 Otsu lakeside Nagisa Park 2.6.8 Naha Shin Toshin 2.6.9 Hokusetsu Sanda Woody Town 2.6.10 Burst of the bubble 2.6.11 Municipal Master Plan 2.6.12 Recovery of the relationship between nature and city 2.6.13 Urban and water designs 2.6.14 Water is still an evident element of urban space 2.6.15 Comparison with Dutch water cities Conclusion 2.7.1 The Japanese Model 2.7.2 Learning from Japan 2.7.2.1 Landscape as leading principle 2.7.2.2 Control and urban design 2.7.2.3 Parallel switch 2.7.2.4 Cultural contradiction 2.7.2.5 Urban design takes over 2.7.2.6 Japanese boldness 2.7.2.7 Public awareness

36 36 38 39 39 40 43 44 45 46 46 48 48 48 49 50 52 54 57 57 57 59 61 63 65 65 66 66 69 71 72 75 77 80 82 82 84 84 85 85 85 86 86 86

Contents

3

4

Historical floods with responding flood control Bianca STALENBERG and Yoshito KIKUMORI 3.1 Introduction 3.2 The Japanese rivers 3.2.1 Geographical characteristics 3.2.2 River classification system 3.2.3 The European river Rhine 3.3 Historical floods 3.3.1 Major floods of the Meiji period (1868–1912) 3.3.2 Major floods of the Taisho/Early Showa period (1912–1945) 3.3.3 Major post World War II floods (1945–1973) 3.3.4 Major floods of the Heisei period (1989-present) 3.4 History of Japanese flood control 3.4.1 Ancient times (River Bureau 1990) 3.4.2 Sengoku period (1478–1602) (River Bureau 1990) 3.4.3 Edo period (1603–1867) (River Bureau 1990) 3.4.4 Meiji period (1868–1912) 3.4.5 Mid Showa period/Post World War II period (1945–1973) 3.4.6 Late Showa period (1974–1988) 3.4.7 Heisei period (1989–present) 3.5 Comparison with Dutch flood control

The development of river management: Tone River Satoshi NAKAZAWA 4.1 River and water management in the pre-modern period 4.2 The beginning of the modern water management in Japan 4.3 The Tone River in the pre-modern era 4.4 The beginning of the modern era of river improvement in the Tone River 4.5 The first improvement work of the Tone River, 1900–1930 4.6 The second plan for the improvement of the Tone River 4.7 The Introduction of the Concept of Kasui To-sei [river water control] 4.8 The appearance of large-scale multipurpose dams 4.9 The third plan for the improvement of the Tone River using multipurpose dams 4.10 Reaction against channel-centered water management and reflection on the river environment 4.11 Conclusion Postscript Acknowledgement

vii

89 89 90 90 91 91 92 93 93 93 94 95 95 95 95 97 97 99 99 100

103 103 103 104 107 108 110 112 112 113 115 117 118 118

viii

5

6

Contents

Urban flood control on the rivers of Tokyo metropolitan Bianca STALENBERG and Yoshito KIKUMORI 5.1 Introduction 5.2 Arakawa floodway 5.2.1 Introduction to the Ara river 5.2.2 Historical Arakawa 5.2.3 The flood of 1910 5.2.4 Principles of a floodway 5.2.5 Specifications of the Arakawa floodway 5.3 The effect of urbanization 5.3.1 Focus on Tokyo 5.3.2 Urbanization in the Netherlands 5.4 Comprehensive flood management 5.4.1 River improvement: Detention basin 5.4.2 River improvement: Artificial underground channel 5.4.3 Damage mitigation measures: Dissemination of information 5.4.4 The Dutch strategy Room for the river 5.5 Super levee: A Japanese concept 5.5.1 Introduction 5.5.2 Specifications of a super levee 5.5.3 Super levees in Tokyo 5.6 Conclusion Stormwater management and multi source water supply in Japan: Innovative approaches to reduce vulnerability Rutger de GRAAF and Jun MATSUSHITA 6.1 Introduction 6.1.1 Historic overview of development of Japanese Urban Water Infrastructure 6.2 Theoretical framework 6.2.1 Threshold capacity 6.2.2 Coping capacity 6.2.3 Recovery capacity 6.2.4 Adaptive capacity 6.3 Complex interactions between vulnerability components 6.4 Dealing with stormwater: Four components to reduce vulnerability 6.4.1 Threshold capacity 6.4.2 Coping capacity measures 6.4.3 Recovery capacity 6.4.4 Adaptive capacity 6.5 Securing water supply: Four components to reduce vulnerability 6.5.1 Threshold capacity 6.5.2 Coping capacity 6.5.3 Recovery capacity 6.5.4 Adaptive capacity

119 119 119 119 120 122 122 122 123 125 127 128 129 132 134 135 136 136 137 138 139

143 143 143 144 144 145 145 145 146 147 149 152 155 157 160 160 161 163 165

Contents

6.6

6.7 6.8 7

8

9

Implementing vulnerability reducing measures 6.6.1 Management of pluvial flooding 6.6.2 Management of water supply Comparison with The Netherlands Concluding

Development of lowland areas Hiroyuki ARAKI and Olivier HOES 7.1 Introduction 7.2 Reclamation of lowlands 7.3 Soil-ripening 7.4 Land subsidence 7.5 Soils and drainage 7.5.1 Lowland soils 7.5.2 Rural and urban drainage 7.6 Concluding remarks Parallel planning approach for urban water management Govert D. GELDOF and Shoichi FUJITA 8.1 Introduction 8.2 Serial and parallel 8.3 The serial approach 8.4 A parallel approach 8.5 Stormwater infiltration 8.7 The implementation of stormwater infiltration 8.8 Interactive implementation Challenges for delta areas in coping with urban floods Chris ZEVENBERGEN and Srikantha HERATH 9.1 Introduction 9.2 Learning from the past 9.2.1 Japan 9.2.2 The Netherlands 9.3 Climate change and the urban context 9.4 Long-term planning 9.5 Flood resilience 9.6 Epilogue

ix

167 167 169 169 172 175 175 175 179 182 186 186 187 190 191 191 191 192 193 194 195 197 201 201 202 202 206 207 208 209 211

References Websites

213 219

Index

221

List of figures

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

1.9 1.10 1.11 1.12 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16

Cities of Japan are located in low parts along the coast and rivers Concentration of assets and population in alluvial plains Urban developments in the Tsurumi River basin over the past 50 years Nihonbashi Bridge and it’s highway fly-over Water balance of Japan, the figure shows a large amount of water is lost as flood runoff, limiting the available water resources Extreme rainfall intensity in Hikone, central Japan U-shaped gutter draining into an urban canal Specific drainage intensities during a flood recorded in the Chikugo River and the Tone River compared with the Tennessee River and the Willamette River, a tributary to the Colombia River Lock in Ara river Change of water quality of the lower Ara River 75th percentile in measured BOD along the Tama River in 1971, 1996 in relation to quality standards Oil balls polluting the beaches in Tokyo Bay Within the urban tissue, due to the sacrosanct family possession, rice paddy fields occur like here in Beppu Ken system Arial view of the Ken landscape with some urbanization Water as self evident element of urban space in Kanazawa Backsides of the lots Map of Tokyo around the year 1900 with one million inhabitants the largest in the world Tokyo 1590–1603 Tokyo 1603–1615 Tokyo 1615–1660 Burcht town Leiden Caste city Edo Entrance to the caste of Edo, Tokyo today Oezu, or ‘great maps’: the Five Kanbun Maps were drawn from such survey maps and newly measured data Waterfronts Watersupply Tokyo The bridge as significant urban element

3 5 5 6 7 9 10

12 12 14 14 15 19 20 20 21 23 24 25 25 25 28 28 29 31 32 33 34

List of figures

2.17 2.18

2.19 2.20 2.21 2.22 2.23 2.24 2.25 2.26 2.27 2.28 2.29 2.30

2.31

2.32 2.33 2.34 2.35 2.36 2.37 2.38 2.39 2.40 2.41 2.42 2.43 2.44 2.45 2.46 2.47

Tokyo (on the right), and other castle cities like Osaka, has just like Dutch polder cities a high centre and low lying expansions Tokyo earthquake reconstruction Land Readjustment District #18 in down town Tokyo east of Tokyo station and bounded on three sides by canals. The upper shows land ownership and road pattern before, and the black of the lower map show new areas of road space after the execution of the project Reroute of infrastructure after the earthquake Comparison with Dutch water cities Plan Zuid Amsterdam Early 1960s an enormous air and water pollution problem came up Gaikaku teibo: the construction of a high concrete wall or dyke along the Sumida River and other canals in the 1960s Highway on water for the Olympic Games in 1964 Highway instead of water for the Olympic Games in 1964 Kenzo Tange’s plan for Tokyo Van den Broek & Bakema for Pampus, 1965 Western part of the General Expansion Plan for Amsterdam by C. van Eesteren (1934) Osdorp Sprawl development in UCA Chiba shows a wide variety of loopholes allowed development to continue in relatively unrestricted manner The mansion-boom also produced great scale differences co-existing in for example Fisherman Warf in Tokyo with the traditional housed on the right surrounded by super high rise In the background the waterfront development from 1980. In the foreground they are preparing the building site of the new island. The picture is taken from the subway making an excellent connection around the new islands Tokyo’s Waterfront Sub Center Plan (1985–1986) on the site of Tokyo Teleport Town Tokyo’s Waterfront Sub Center Plan (1985–1986) on the site of Tokyo Teleport Town Hachioji Minamino City Otsu lakeside Nagisa Park Naha Shin Toshin Hokusetsu Sanda Woody Town Sun Varie Sakurazutsumi (in Musashino-shi, Tokyo) New urban block in Saga Traditional roofs in Kanazawa Traditional rain water discharge gutter in Kyoto Rain water discharge integrated in the pavement (around the Tokyo Dome), being kept clean extremely well Small canal in Kanazawa Canal as part of public space in Kanazawa Water square in the park near the castle in Tokyo Water as backyard in IJburg Streets are kept clean and plants make them more liveable

xi

35

41 42 47 49 50 51 52 53 53 55 56 58

62

64 65 66 67 68 69 70 74 77 77 78 78 79 79 80 82 84

xii

2.48

2.49 3.1 3.2 3.3 3.4 3.5 3.6 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14 6.1

6.2 6.3 6.4

List of figures

Poster to make the inhabitants of Tokyo aware of the fact that fat spooled through the sink will end up as white balls in the water that will disturbed the wastewater treatment plant Before used as flush water, the water can be used to wash hands after using the toilet Failure mechanisms of soil structures A typical Japanese River River IJssel; one of the Rhine branches Kiso River in the eighteenth century Plans for construction of Arakawa floodway Room for the river measures Relief map of the Kanto Plain Estimated river basins 1600 1867 Plan1900 Plan1910 Plan1941 Inundated area 1947 Plan1949 Plan1980 2000 Ara River: length and width Principles of a floodway Current course of the Arakawa floodway Tokyo in 1909, 1954 and 1996 Position of rivers in Tokyo Concept of Comprehensive flood management Principles of a detention basin Tsurumi multipurpose detention basin Flow Rate Distribution The river is allowed to overflow at the overflow location in the event of flooding Artificial underground channel Retaining, storing and draining of water Conventional dike and super levee Super levees along the Sumida River and Ara River The four components and three domains of the vulnerability framework illustrated by a damage return period graph. The three domains are interrelated, changes in one domain affect the other domains, resulting in an overall change in vulnerability The process of land subsidence in Tokyo Location of the Naka and Ayase urban rivershed, the terrain level is lower than the river level, this is similar to Dutch urban polders Examples of Best Management Practices to improve the current combined sewer system in Tokyo under the New Quick Plan for improvements of the combined sewer system

87 87 90 91 92 96 98 101 105 105 106 108 109 111 114 114 115 117 120 123 124 126 127 128 130 131 132 133 134 136 137 139

147 150 151

153

List of figures

6.5 6.6 6.7

6.8 6.9 6.10 6.11 6.12

6.13 6.14 6.15 6.16 6.17

6.18 6.19 6.20 6.21

7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 8.1 8.2 8.3 8.4 8.5 9.1

Reducing damage in case of flooding: high level difference between road level and floor level Reducing damage in case of flooding: elevated first floor Improving recovery capacity by accessibility. Lock along the Arakawa, designed to enable the transport of goods into the central area of Tokyo after a disaster Detail of street infiltration box Illustration of Experimental Sewer System in Tokyo Adapting urban development to the natural water cycle in a new town area Scheme of the Japanese flood forecast system to effectively reduce flood damage River water resources in the region fo Tokyo Metropolitan Area, dotted lines show the water transfers between rivers that can be used during droughts Location of emergency water supply bases in the city of Tokyo, on the right side of the map, Tokyo Bay Treatment scheme of runoff and recycled water in Tokyo Dome Tokyo Dome Stormwater utilization scheme in a Japanese house Multiple uses of recycled water in the urban environment such as road cleaning, sewer cleaning, park irrigation, cooling of pavement and urban stream restoration Total Framework for basin management systems On-site type storm water runoff reduction In-house recycling systems Change of water consumption in Japan (1950s–2000s), water consumption per capita stabilized around 300 liter per capita per day, leading to an annual water consumption of 16 km3 Japan covers 330,000 km2 and has a 30,000 km coastline Hachirogata polder (North-West Honshu) Polders in Japan constructed after WW II Vertical ripening cracks below 0.5 and 1.0 m below surface level Lake bottom in The Netherlands just after reclamation The intergranular pressure increases by reclamation Change of ground water potential in Tokyo History of ground subsidence in typical areas Standard phasing of a project (serial approach) Kitazawa Double-Deck river Kitazawa river The principle of working parallel in Interactive Implementation. The activities are on the vertical axis; time on the horizontal axis Nijmegen Stikke Hezelstraat Adapting to climate change: substitution of built components and structures

xiii

155 156

156 158 159 160 161

162 163 164 164 165

166 168 170 171

171 176 178 180 182 183 184 186 187 192 198 198 199 199 209

List of tables

2.1 3.1 3.2 5.1 6.1

6.2

7.1 7.2 7.3 9.1

Evolution of Japanese land use zoning categories Comparison of a Japanese river with a European river Major floods in the period 1945–1959 Delta cities in Japan and The Netherlands Description of type, hazard frequency, time orientation, uncertainty and responsibility of the four components of the vulnerability framework Overview of vulnerability decreasing measures for water supply and pluvial flood control classified according to the four components of vulnerability Zuiderzee polders in the Netherlands Polders in Japan constructed after WW II Design precipitation with a 1/10 year return period Key features of the direction of the transition towards the resilient approach

73 92 94 125

144

148 178 181 190 210

Chapter 1

Introduction Frans van de VEN 1 , Hiroaki FURUMAI 2 and Kenichi KOGA 3 1

Section of Water Resources, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands and Market team Urban Water Management of Deltares 2 Department of Urban Engineering, The University of Tokyo, Japan 3 Department of Civil Engineering, Saga University, Saga, Japan

Geography of Japan Japan is an island nation in East Asia comprising a large stratovolcanic archipelago extending along the Pacific coast of Asia. Measured from the geographic coordinate system, Japan is 36° north of the equator and 138° east of the Prime Meridian. The country is north-northeast of China and Taiwan (separated by the East China Sea) and slightly east of Korea (separated by the Sea of Japan).The country is south of Siberia in Russia. The number of inhabitants of Japan was 123,6 million in 1991. Average population density is 327 inhabitants per km2. The main islands, sometimes called the ‘Home Islands’, are (from north to south) Hokkaido–, Honshu– (the ‘mainland’), Shikoku and Kyu–shu–. There are also about 3,000 smaller islands, including Okinawa, and islets, some inhabited and others uninhabited. In total, as of 2006, Japan’s territory is 377,727 km2, of which 13.200 km2 is water surface (Ministry of Land, Infrastructure, Transport and Tourism, the River Bureau, 2008). Japan’s area has been steadily increasing due to construction of artificial islands.This makes Japan’s total area slightly smaller than the U.S. state of Montana. Japan is bigger than Germany, Malaysia, New Zealand and the U.K., and is 1.7 times the size of Korea and 10 times the size of Taiwan (Wikipedia). Japan is nine and a half times larger than the Netherlands. Its topography consists basically of mountains and polder land. ● ● ● ●

mountains (61%) hills (12%) terraces (11%) plains (16%)

Land use is mostly forest (67%); agriculture (14%) residential, commercial and industrial areas (4,4% or 16.500 km2).The plains are almost exclusively used as rice paddy or for urban areas. The Japanese mountains and hills are not fit for habitation (Yoshimura, Omura, Furumai and Tockner (2005, 94). About 65 % of the country has slopes steeper than 14%. In the central area of Honshu, mountains are found in the 3, 000 meter group. Approximately 7% of these mountains are volcanic (Takahashi and Uitto, 2004, 63).The mountain area is composed of sedimentary rock, sandstone, chert and limestone (Yoshimura et al., 2005, 95).The plains are composed of river sediment resulting in unstable and soft ground. Geologically speaking Japan is a young country with frequent earthquakes and numerous volcanoes. Japan is located in the CircumPacific Ring Volcanic Belt and has 200 volcanoes of which 78 are active. Earthquakes are a regular phenomenon; about every couple of decades Japan is hit by a quake stronger than 7.0 on the Richter scale.

2

Urban water in Japan Due to the natural environment and human interventions in particular the lowlands and flood plains are densely populated.They cover less than 10% of the land, but contain 51% of the population and 75% of the assets (Nakamura et al., 2006, 420). Areas below sea level in the three major bays of Japan (Tokyo, Ise and Osaka Bays) occupy an area of 577 km2 and accommodate 4.04 million people (Ministry of Land, Infrastructure,Transport and Tourism, the River Bureau, 2007). Besides the attractive topographical location of the low lying areas, the flood plains are also ideal for agriculture.The Japanese have been involved in rice farming for more than 2000 years (Yoshimura et al., 2005, 93). In alluvial plains, formed by floods, people settled in areas where river water was easily available for irrigation. Rice farming transformed the alluvial plains into paddy fields. A side effect of living in these alluvial plains is the constant threat of floods. The Japanese are, however, persistent in staying.To date, both population and industry have been thriving in the flood plain areas of rivers where the danger of flood disasters remains latently (Infrastructure Development Institute-Japan and Japan River Association, 12).

Meteorological conditions Japan is situated in the East monsoon region with a warm and humid climate (Yoshimura et al., 2005, 95). Japan has twice as much precipitation as the world average (Infrastructure Development Institute-Japan and Japan River Association, 8). The mean annual precipitation in Japan is approximately 1,800mm, whereas in some areas precipitation of 3,000mm can be reached (River Bureau, 1990, 70). Large precipitation takes place during the rainy season in June and early July, during the typhoon season in September and October with typhoons originating from the southern Pacific, and during winter snowfall occurs in northern Japan (Yoshimura et al., 2005, 96). Snowfall causes prolonged snowmelt floods in spring in the northern part of Japan (Ikeda and Yoshitani, 2006, 1252). Generally speaking, the dry seasons are from December to March in winter and from the middle of July to the end of August in summer.The Japanese climate is less favourable for wind power utilization.

1.1 A CHALLENGING TASK Urban water managers in Japan are facing many challenges. Water is a highly valued element in urban areas, while at the same time posing a burden and a risk. Large parts of Japan’s cities are located in lowlands along the coast or in the floodplain of a river as illustrated in Figure 1.1. As a result, surface water is a common element of the urban landscape; urban rivers, canals, brooks and ditches drain the urban area. Life in these cities is intensively interrelated with this water, as it was in the past. Economic development in the harbour region, shipping goods and transporting people, providing a scene for many cultural events, a way to discharge pollution, a source for water supply, fishing grounds, water for fire fighting and many other functions are served. Yet, urban water systems are stressed and threatened by a large number of natural and human factors. ●

Ongoing urbanization itself is the first stressor to mention; water demand and often water pollution aggravate the water resources management problems.

Introduction

3

Figure 1.1 Cities of Japan are located in low parts along the coast and rivers Source: Ministry of Land, Infrastructure and Transportation: Rivers in Japan, 2005

●

●

●

●

Intensive rainfall, related to typhoons or stationary frontal rains, produces flooding due to overtopping or breaching of dikes or floodwalls or due to insufficient drainage capacity to handle such a massive downpour. Flash response of rivers to rainfall, due to their steep gradients and short distances. Earthquakes, tsunamis and high tides prompted by typhoons create a threat to all activities in the coastal and riparian zones. Flood safety provided by the dikes is at risk due to these natural phenomena. Droughts and heat are threatening human, animal and plant life in cities. The urban heat island aggravates this problem.

4

Urban water in Japan

●

Intensive industrial activity leads to accidental pollution spills, even though control of these catastrophes has improved significantly. In an earthquake – prone country like Japan accidental spills are inevitable after a severe quake. Landownership impairs corrective measures that require space.

●

These phenomena are most eminent in central and west Japan, on Honshu and Kyushu island. But also the northern part of Japan, Hokkaido, has to deal with extreme conditions every now and then. That is why the Japanese have adapted and have learned to live with these threats. It has become part of their design practice and even their lifestyle. We will focus this book on urban drainage solutions in the central and south western part of the country, as we can learn a lot from all the experiences obtained there.

1.2 URBANIZATION Japan’s urban areas continue to extend, even though the availability of usable land for urban development is very limited. The majority of Japan is occupied by steep mountains. Only 26% of the land, some 94,250 km2 is available for housing the approximately 128 million inhabitants, for agricultural activities, industrial activities, parks and other green areas within the living and working environments. 75% of Japan’s assets are concentrated on 10% of the land surface, mainly in low-lying areas that are exposed to flood risks from rivers and sea. Japan has a city planning law to regulate urban development. This law is however not very strict at the larger scale of urbanization. As a consequence, cities expand gradually by developing on rice paddies. The fields are raised, drains installed and a street laid, and houses are built as close together as possible on both sides of the street. The cities fan out in this way and merge into paddies with the occasional couple of houses on a fully developed field. Villages as such do not exist. The reason for the absence of large-scale planning is the power of the private landowners. The possession of a paddy field is vitally important for a family. Family possession is sacrosanct, not only because of the economic importance of growing rice, but also for spiritual reasons. As a result it is almost impossible to realise urban development plans of any size; and the gradual expansion means that paddies persist within the city boundaries because families refuse to build on or to sell them. Areas designated for urbanization show an average annual population increase of 8.6% (Ministry of Land, Infrastructure and Transport, City Planning annual report, 2002). Solution to this need for more urban floorspace is sought in height and depth of buildings, rather than in a further extension of the existing urban area. Yet, urbanization progresses slowly, as illustrated in Figure 1.2, showing the growth of urban area in the catchment of the Tsurumi River Basin in the Kanagawa Prefecture, Yokohama. By 1958 this area was over 90% rural; by 1997 rural land had decreased to about 15% of the basin. Paddy fields were converted to housing lots, in most cases one by one. A peculiar result of this gradual development is, that the regional drainage system of small ditches is often retained in these new urban areas. Only after a while, when the population pressure becomes higher, are these ditches covered and turned into culverts and pipes.

Introduction

5

Figure 1.2 Concentration of assets and population in alluvial plains Source: Ministry of Land, Infrastructure and Transportation: Rivers in Japan, 2005

Figure 1.3 Urban developments in the Tsurumi River basin over the past 50 years Source: Ministry of Land, Infrastructure and Transportation: Rivers in Japan, 2005

Tokyo provides a good illustration. Once, the lower part of the city was Japan’s largest water town. Tokyo was mentioned in the same breath as Venice, Amsterdam and St. Petersburg. It is still possible to visit Tokyo’s origins, the castle town of Edo, or ‘the high city’ (yamanote), situated on a ridge, and look out over the adjacent delta where ‘the ordinary folk’ lived in the ‘low city’ (shitamachi), reclaimed from the water. Like Amsterdam, canals were dug in the low city to drain the land and there were also harbours and warehouses. This was the site of most of the business activity and the city’s entertainment. Floating theatres and ceremonies on the water were important cultural aspects that made life in the low city extremely popular. This city was devastated by an earthquake in 1923. The municipal administration then had a unique opportunity to implement a new street plan, suitable for the car.

6


The system of gradual expansion continued however, and yielded a fascinating cityscape full of differences in scale and functional combinations. This mosaic is normal for the Japanese urban areas. The barrier to large-scale plans did become a problem when Tokyo was selected as the venue for the 1964 Olympic Games. The city had to improve its main road infrastructure by introducing a modern highway system. The power of private landownership formed a barrier, and the only way around it was to lead the roads over the water. That is why one encounters many elevated highways, standing on pillars in rivers and canals in the city, or catches a glimpse under an old bridge of traffic flashing by on a highway on the bed of what was once a watercourse (Figure 1.4). Tokyo’s original water town is concealed behind enormous concrete pillars and flyovers, but has not been lost. Tokyo’s most important historic bridge, the Nihonbashi, with its ancient features, simply plays its part in the ultra congested traffic, and has been covered by an enormous expressway. And just as in the Netherlands, where historic urban watercourses are being reconstructed to open up the congested urban landscape, the Japanese are also interested in Tokyo’s historic identity, and are planning to make the bridge ‘expressway free’. The installation of a dense and effective public transport system and the stricter banning of private cars from inner city environments gradually make these urban landscape (re)developments feasible. Many new urban extensions are unfortunately situated in areas less favourable for urban development. Some cities develop in more mountainous regions, but other new sections develop into lower, more flood-prone parts of lowlands and alluvial plains or on newly reclaimed land, such as Osaka Airport and the reclaimed lands in Tokyo Bay and the Ariake Sea.

Figure 1.4 Nihonbashi Bridge and it’s highway fly-over Source: Fransje Hooimeijer

Introduction

7

Step by step the natural discharge capacity of the rivers and the available storage capacity for retaining stormwater and flood flows was reduced by this urbanization process. This makes the cities gradually more vulnerable to flooding, especially if we take into consideration that not only the risk grows, but also the potential damage. Figures of the economic flood damage have increased to billions of Yen annually, not to mention the loss of lives. 1.2.1 Water resources and water use The average precipitation is Japan is 1800 mm, whereas the world average is about 800 mm. However, the variations from year to year are considerable. Although the amount of precipitation in Japan is high, the amount of precipitation per capita is low, about 5200 m3/capita which is less than one fifth of the world average. No wonder the country suffers from severe droughts every now and than, interrupting the regular domestic water supply to cities. The need for other water sources is evident. As Japan has no water sources from international rivers and because natural water resources distribution varies considerably in time and space, management of these resources is

Figure 1.5 Water balance of Japan, the figure shows a large amount of water is lost as flood runoff, limiting the available water resources Source: Ministry of Land, Infrastructure and Transport, Water Resources in Japan, 2002

8


essential. The total rainfall in Japan is 650 km3 in an average year. Due to rapid runoff only a limited amount is available for water resources. The total average yearly evaporation is 230 km3. The total flood runoff amounts to 210 km3, hence, the total potential available water resources quantity is 210 km3. A total quantity of 86 km3 is used for various human purposes. Agriculture and fishery is the main water user with a total water quantity of 57 km3, followed directly by industrial water use that amounts to 13 km3. Yearly domestic water use is 16.3 km3, of which 13 km3 is treated in wastewater treatment plants (MLIT, 2002). Of the 86 km3 that is used approximately 87% is obtained from rivers and lakes, while the remaining part is extracted from groundwater. Urbanization has led to a giant increase in water demand for drinking water, industrial water and irrigation. Urban water consumption per capita has shown a giant increase over the past five decades. Modern lifestyle and sanitary equipment require much water. Japanese people use on average about 330 l/cap/day for domestic use; total usage including industry, hospitals, hotels and so on is about 600 l/cap/day, compared to 130 l/cap/day in the Netherlands. In response to industrial development and population increase in urban areas, seven river systems were designated as water resources development river system. These are Tone river, Arakawa River, Toyokawa River, Kiso River, Yodogawa River, Yoshino River and Chikugo River (Ministry of Land, Infrastructure and Transport, 2002–2004). In each of these river systems, a water resources development plan has been made, and comprehensive development and rational use of water resources are stimulated. Water for drinking and irrigation was traditionally supplied to the cities by small streams, canals and channels. These were also used for shipping transport. With the introduction of a piped water supply part of these surface waters has disappeared in big cities; in the smaller and more rural cities these surface water supply systems however still exist. 1.2.2 The value of water The cities’ inhabitants highly value the presence of water in their living environment. Strolling along the water, fishing, and paddling are popular forms of recreation. Even the sound of water is appreciated, as reflected in the famous haiku of Matsuo Basho: furu ike ya kawazu tobikomu mizu no oto

O, old pond A frog jumps Sound of water

And numerous cultural events are related to water. People go on the river with boats and lanterns or enjoy fireworks from the river bank. That is why even small streams and canals are intensively landscaped.

1.3 PRECIPITATION The pretty face of the Japanese has a reverse side. Rainfall can turn into tremendous downpours during the typhoons that hit Japan’s cities with clock-like regularity. Also

Introduction

9

stationary frontal rainstorms can drench cities and produce serious flooding. About three typhoons hit Japan directly each year. For example, due to typhoon Kathleen that struck Japan in September 1947, several dike breaches occurred. The embankment of the Tone River collapsed about seven km upstream of Tokyo. The resultant flood flow reached as far as the Tokyo metropolitan area (River Bureau, 1990, 12). It is therefore not a surprise that the Japanese rivers feed themselves with rain. The total direct flood damage, pluvial and fluvial, was in 2000 about 6.5 times as much as fire damage (Infrastructure Development Institute-Japan and Japan River Association, 11). Several times per year hourly rainfall intensities of over 100 mm are recorded; intensities between 75 and 100 mm/h are recorded up to 46 times per year since 1990. The maximum daily amount of rainfall of 421 mm has led to a catastrophic flood disaster in Niigata Prefecture.

1.4 DRAINAGE Drainage capacity of the street surface is adapted to these extreme conditions. Large U-shaped gutters drain runoff to the urban canals or to large evacuation drains, as shown in Figure 1.6. The design discharge capacity for paved surfaces ranges between 50 and 90 mm/hr, based on return period 5–10 years (Dijk, 1994). And even with these large drains it is considered wise to elevate the floor of your house high over street level, so that ponding storm water cannot enter the property. Floor level (‘tatami’ level) is around 0.25 or 0.30 m above ground level. This and other ways of damage prevention are important for all inhabitants, because getting any flood damage compensation is not possible, neither from insurances on the commercial market, nor from government. The Severe Disaster Relief Act (1976) is only used in case of severe national disasters. Droughts, often in combination with high temperatures, can disrupt urban life and turn into torture for the citizens when the water supply gets interrupted, in particular in densely built up urban areas. Famous is the Fukuoka drought in 1978, persisting for 287 days, affecting over 3 million people and leading to the evacuation of people from the area. The disaster has led to significant investments, in order to reduce its vulnerability to drought. In 1994 the same area was hit by a drought lasting 295 days, but

Figure 1.6 Extreme rainfall intensity in Hikone, central Japan Source: Ministry of Land, Infrastructure and Transportation: Rivers in Japan, 2005

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the effect was much less destructive because an aqueduct from the Chikugo River and other measures were installed at that time. In houses, living conditions during these hot dry periods are kept pleasant by air conditioners; outdoor conditions however can get harsh. In order to reduce the urban heat island effect first full-scale experiments with sprinkling sewage treatment effluent on the street surface are running now in Tokyo.

1.5 FLASH RESPONSE OF RIVERS High precipitation intensities during one or several days result in urban flood risk because of the internal urban drainage system; the most important flood threat for the many urban areas located in alluvial plains and in lowlands are however the rivers passing through the city. Japans rivers are all short and steep. Only a few reach over 200 km and most sources are located over 800 m above mean sea level. Moreover, the most upstream part of the basins is steep mountainous, covered with bedrock. Natural retention is minimal there. It is only by the creation of numerous dams that this retention became of some importance. The fast response of the rivers is well illustrated in Figure 1.7, showing the specific drainage intensities of two large Japanese basins with two American ones during major floods. The limited natural storage capacity leads to extreme ratios between low flow and flood flow discharges. A ratio of 100 is not exceptional, while this is about 10 for the Rhine River. The ratio between the discharge and the precipitation, runoff ratio in short, is very high and varies between 0.6 and 1.0 (Yoshimura et al., 2005, 96). The limited low flows allow vegetation to develop rampant in the riverbed, producing significant friction during sudden floods. Maintenance of the riverbed is therefore a first concern.

Figure 1.7 U-shaped gutter draining into an urban canal Source: Rutger de Graaf

Introduction

11

Due to the flash type of flood the early warning lead time and so the response time for flood prevention and preparedness is limited to often much less than 12 hours. Evacuation time for people from river flooding is estimated at two or three hours. That makes evacuation of citizens before a flood comes in almost impossible. People primarily trust on the system of dikes and levies, dams, floodways and retention areas for their safety against flooding. This system is generally designed for a return period of 100 years, sometimes up to 200 years. Any more extreme storm event will overtop dikes and dams and result in flooding, often in densely populated areas. Evacuation routes to local safe havens such as mounts or high buildings are sometimes provided, together with instructions on how to respond to flood warnings and flooding. Japan is now implementing a comprehensive flood control strategy, aimed not only at river improvement but also at runoff control and damage mitigation measures; runoff control does not only comprise the construction of more retarding basins; it entails a total restructuring of the drainage system of each catchment, both in the rural and the urban areas, aimed at flood proofing these environments. This development is discussed extensively in the remainder of this book.

1.6 EARTHQUAKES AND TSUNAMIS Earthquakes do not only cause massive destruction within cities but can also damage the flood protection structures or can even cause dike breaches. Floods are the result. The Great Kanto earthquake in 1923 caused for instance broken and cracked embankments along the Arakawa floodway on 28 spots (Arakawa – Karyu River Office and (MLIT, 2006, 47)). Earthquakes also trigger surges and floodwaves along the coast (tsunami’s). And as many cities are located along the coast, near river mouths and harbours, these surges produce a serious threat to the safety of the cities inhabitants. Coastal defence has therefore always been a top priority in Japan. At some points the coastline length was reduced by closing of bays and river estuaries. Fierce concrete floodwalls were build, with wave breaker structures to dissipate energy of the rolling waves. The design level of these coastal levees is a derivative of the observed flood levels during typhoons and tsunamis. Along the mouth of the Yodo River near Osaka the design level includes 3 meters for wind set up and 3 meters for wave run up. Protection against tsunamis and floods cannot be provided with strong dikes alone. An intensive tsunami flood warning system is operational 24 hours per day. All means of telecommunication are used to warn people in the endangered zone; response time is short, sometimes less than one hour. Evacuation routes for residents of the flood endangered zone are prepared and well indicated. And many people are trained to assist during an evacuation of flood prone areas and underground facilities. This is all part of the flood hazard mapping and flood risk management procedures. Preparedness for natural disasters even goes beyond this risk. For example, the ship lock in the Ara river in Tokyo (Figure 1.9) is constructed in such a way that ships can be locked through very rapidly, so that in case of a calamity ships with relief supplies and ships to evacuate people can quickly enter and exit the area.

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Figure 1.8 Specific drainage intensities during a flood recorded in the Chikugo River and the Tone River compared with the Tennessee River and the Willamette River, a tributary to the Colombia River Source: Ministry of Land, Infrastructure and Transportation: Rivers in Japan, 2005

Figure 1.9 Lock in Ara river Source: Fransje Hooimeijer

Japans ways to protect urban areas for increased risk of flooding and droughts due to climate change follows the very same lines as its protection against typhoons, earthquakes and tsunamis (Ministry of Land, Infrastructure, Transport and Tourism, 2007).

Introduction

13

1.7 WATER QUALITY A first ecological revolution took place in Japan in the 1970s, after the oil crisis and several environmental incidents. Greater regard for the quality of water was achieved. This was followed by a second change in the mid 1990s, when the water managers actively started working on the ecological recovery of rivers and streams. The environmental awareness and the responsibility of the general public for the environment are impressive. Both land and water are spotlessly clean, and they have a variety of projects and methods to keep them so. Communication and awareness campaigns are widely used instruments. It is now widely recognized that surface waters need a good quality to serve the many functions that they are expected to. Preservation of the river environment and ecological recovery of streams are top priorities in surface water and river management nowadays; priorities that are strongly supported by citizens yearning for an enjoyable, natural waterfront environment. Large scale ecological recovery programmes are now being implemented in the rivers and urban canal systems. The primary function of the urban watercourses in Japan is however to drain surplus stormwater – unlike the situation in the Netherlands, where the primary function is to retain stormwater. Japan was relatively late in constructing sewers in its densely built up urban areas: by 1990 only about 75% of all houses were connected to a sewerage system, but nowadays this rate is over 98%. About 68% of this water is treated before discharge into the river or via sea outfalls. About 70% of all sewerage systems are separate sewers. Stormwater sewers convey the runoff from streets, roofs and parking areas and other areas to the urban ditches, canals and stormwater drains. As a result, pollution collected in the rain or on the surface is washed into the surface waters. Wastewater is collected in a separate pipe and conveyed to a treatment plant. About 30% of the sewerage systems is of the combined type; stormwater and wastewater are both drained to the treatment plant but during heavy storms a mixture of wastewater, stormwater and sewer sludge is discharged into the urban watercourses by overflow structures. Much attention is being paid now to reducing emissions from the sewer systems and to the reduction of flow peaks by source control measures. Stormwater retention and infiltration is used more and more nowadays to retain water and pollutants on the spot. A significant problem of the urban rivers are their low flow conditions. Because of their nature low flow runs to almost zero during dry spells. As a consequence some rivers drain only the effluent of the wastewater treatment plants; the quality of this river water is determined completely by the quality of the treatment process. Other rivers fall dry during long periods of drought, as the effluent of many treatment plants is discharged directly into the sea or at least very close to the river mouth. In many urban areas small paddy fields are scattered between houses, offices and factories; and fields of lotus grow in urban ponds. This agricultural form of land use can have significant influence on the water quality in the whole system, as fertilizers and pesticides are intensively used. A typical Japanese water quality problem is the oil balls emitted by combined sewer overflows. They were a plague to people recreating on the beaches along Tokyo Bay. This problem was first of all attacked by public information: advertisements informed the people about the consequences of discharging waste broiling fat in the sewer system.

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Figure 1.10 Change of water quality of the lower Ara River Source: Arakawa Karyu River Office

Figure 1.11 75th percentile in measured BOD along the Tama River in 1971, 1996 in relation to quality standards Source: Wagner et al., 2002

Introduction

15

Figure 1.12 Oil balls polluting the beaches in Tokyo Bay Source: Tokyo Metropolitan Government

But in addition a treatment plant was started up to supply part of the beach with clean swimming water. A screen prevents the mixing of polluted water from the bay with the treated water; swimming water quality is monitored continuously to safeguard the health of the bathing guests. The results of this facility are now being evaluated to decide about its need for continuation. Information about the quality of the bed sediments in urban surface water is available only for experimental sites. The same holds for pollution of the water courses by accidental spills and for the ecological quality of the surface waters. The introduction of the Water Framework Directive in Europe has boosted ecological monitoring and ecological recovery programmes. It is interesting that without the influence of such a directive the monitoring of the chemical and ecological status of surface waters in Japan and its ecological recovery program is developing in other directions (Ministry of Land, Infrastructure, Transport the River Bureau, 2008).

1.8 CONCLUDING The very dense urbanization in Japan in combination with the characteristics of the country and with the natural hazards that the Japanese people have to cope with make urban drainage a hard job. Providing good flood protection, an ample water supply, sufficient drainage of stormwater and wastewater and a good water quality of surface waters and of groundwater is a complex problem. Simple solutions are often ineffective. That is why new, innovative solutions were developed and implemented. This took time, but Japan’s water managers and engineers managed to develop interesting new ways of urban drainage and water supply during the past decades. Ways that are

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interesting for – and inspiring to – colleagues from abroad, to find new, more sustainable ways for urban water management; other ways to adapt to climate change, other ways to live with water, with shortages of water and with water quality issues. Differences in approach include: ● ● ●

●

● ●

●

fast drainage in Japan versus water retention in the Netherlands, reuse of treatment plant effluent versus reduction of water consumption, drainage by networks of small watercourses versus drainage by large main canals and brooks, focus on public awareness and source control for pollution prevention rather than on end of pipe treatment, focus on surface water systems rather than on urban groundwater, focus on coping capacity and recovery capacity with natural hazards, rather than on prevention of damage alone, at all costs, Focus on very extreme conditions like typhoons and droughts, which seems to make attention for the gradual change of conditions brought by climate change and sea level rise less urgent than in the Netherlands. Policy development on this topic started in Japan much later than in the Netherlands or in the UK (Ministry of Land, Infrastructure, Transport and Tourism, 2007).

There are similarities too. The precious value of water, in particular its emotional, spiritual and aesthetical value is recognized in both countries. Urban water landscapes are designed with care and flair. Sustainable use of our limited water resources is to strive for, and deterioration of the chemical and ecological water quality is not tolerable. This publication starts with the historical relation between water and urbanism in Japan (chapter 2) and the history of floods and how the Japanese responded with flood control (chapter 3). Two case studies of urbanization of rivers follow, the development of river management: Tone river (chapter 4) and Urban flood control on the rivers of Tokyo Metropolitan, Ara river (chapter 5). Chapter 6 is studying stormwater management and multi source water supply in relation to the vulnerability theory. The more technical groundwork of urbanization in the lowlands are described in chapter 7. The processes of water management in the Netherlands and Japan are compared in chapter 8 taking two case studies. The concluding chapter ties everything together in final remarks that sets out the challenges for delta areas in coping with urban floods.

Chapter 2

History of urban water in Japan Fransje HOOIMEIJER Department of Urban Design, Faculty of Architecture, Delft University of Technology, The Netherlands

2.1 INTRODUCTION Japan has no urban design, and no large-scale plans for streets, squares and houses with gardens. Instead, the cities expand gradually by developing on rice paddies. The fields are raised, drains installed and a street laid, and houses built as tightly together as possible on both sides of the street. The cities fan out in this way and merge into paddies with the occasional couple of houses or a fully developed field. The reason for the absence of large-scale planning is the power of the private landowners. The possession of a paddy is vitally important for a family. Family possession is sacrosanct and is how people make a living – the price of rice in Japan is kept artificially high – and where they live. It is therefore almost impossible to develop plans of any size, and the gradual expansion means that paddies persist within the city because families refuse to build on or sell them. A major advantage of this planless urban expansion, compared with the Dutch situation, is that it retains the national water systems, which are a conspicuous part of the city. This chapter shows the relationship between urban planning and water management in Japan and makes the comparison to the situation in the Netherlands. Because Japan has been very centrally organized all planning efforts were based on the problems in Tokyo. Therefore it is suitable to take Tokyo as main example of urbanism in Japan. Also as a water city and geographical situation it was and is very comparable to Amsterdam. There may even be more similarities than are considered here. 2.1.1 Succession of systems The history of Japan is ordered in eras named after the type of government or emperor. The first era in this story is Tokugawa 1603–1867, then Meiji 1868–1912, Taisho1912–1926, the Sho-wa era (Enlightened Peace) 1926–1989 and Heisei era that started on January 8, 1989 when Akihito, the current emperor of Japan succeeded to the throne, after the death of his father, Hirohito, the Sho-wa Emperor. The Tokugawa period 1603–1867 was a feudal military dictatorship of Japan established by the shoguns (generals) of the Tokugawa family. This period is also known as the Edo period, after the capital city of Edo, now Tokyo. In the seventeenth century Japan was a booming agricultural en economical country, with a fast growing population number (Sorensen, 2002, 12). The effective administrative control over the state was via land and population, and not through buildings and infrastructure. The pressure on space was such that open space was hard to protect and always was subject of negotiation and a certain give and take (Sorensen, 2002, 25).

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Instead of the process from feudalism via independent self-governing cities towards industrial cities, in Japan the single step from feudalism to industrialism was made within a few decades after the Tokugawa period ended in 1867. In 1868 the Japanese emperors retook power from the Tokugawa shoguns in what is named the Meiji Restoration. The end of the Edo period is illustrated by renaming Edo to Tokyo. The Meiji era (Period of Enlightened Rule) that followed stands for a different type of social construction toward more democratic participation in government. Under pressure of the colonization of the surrounding countries the Japanese reformed their society from a feudal structure into an empire. The industrial development began with a global study trip from which much was learned and indeed improved upon. In the United States industry was studied, in England the railway system, in Germany medicine and in the Netherlands hydraulic construction. After Meiji the Sho-wa (1926–1989) and Heisei era (1989–today) followed. The most significant breaks in time for the story of urban water in Japan, however, are in the twentieth century not the change in emperor but ending of the Pacific War in 1945 and the oil crisis in 1973. The build up of this chapter is therefore ordered correspondingly. 2.1.2 Urban planning Two related characteristics of urban Japan are the intense intermingling of differing land uses and the extensive areas of unplanned, haphazard urban development. It is hard to believe that a land use zoning instrument was in use since 1919 (Sorensen, 2002, 2) because it has had no effect on the shape and patterns of cities on the one hand, or in developing planning system on the other. One of the reasons for the absence of planning or urban design in Japan is the absence of a civil society. The definition of civil society being a set of institutions, professional organizations and behaviours situated in between the state, the business world and the families, including non-profit and philanthropic institutions, social and political movements (Sorensen, 2002, 8). These parties work bottom up, directing the needs and demands from the citizens towards the government. During the Tokugawa period there was a strong top-down government, characteristic to the feudal construction. The people were there for the national state, not the other way around. Somehow this top-down construction survived the Meiji Restoration and was kept alive with a total centrally organized government. An important aspect that kept this top-down approach of planning alive was the importance put on landownership by the succeeding governments. Landownership rights are rooted in a long tradition of control over land and its productive capacity as the basis for political and social power, a feudal socio-political organization which in Japan lasted until the end of the nineteenth century (Sorensen, 2002, 108). The importance of landownership is still a great power even till today and an important dilemma as we will learn later, in making overall urban designs let alone plan an area. In Japan planned urban development is usually laid out in grids or modified grids scattered amongst unplanned development along artery roads that follow the natural topographical characteristics, and patterns of earlier agricultural development (Sorensen, 2002, 36). The existence of rice paddy fields in the middle of a city is no exception.

History of urban water in Japan

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Figure 2.1 Within the urban tissue, due to the sacrosanct family possession, rice paddy fields occur like here in Beppu Source: Fransje Hooimeijer

2.1.3 The Tan as principle dimension for the city The structure of the water system, or the irrigation system, shaping the Japanese paddy fields is taken from the Chinese land subdivision system, adapted in the seventh century (Arakawa-Karyu River Office, 2004, 21). In the sixteenth and seventeenth century the development of rice paddy fields expanded by the use of fertilizer and the improving of flood planes (Arakawa-Karyu River Office, 2004, 21). The measurements of the main grid was 60 by 60 ken (1 ken 1,818 meter). Each block was 109 109 meters and called a cho-. These were again divided in twelve sections producing the individual paddy fields with the size of the tan: 18 54.5 981 square meter. Since the cities grew simply by filling in these paddy fields these are also the dimensions in the cities. The field was raised and given one street with houses on both sides. This did not produce a road system but a pattern of rural streets enclosing dead end units. This fitted well with the close-knit social construction of the Japanese who are organised in these small cells. It is a system of spatial nesting, that is, a hierarchy of urban areas nested within each other. This is also expressed in the fact that in Japan the streets have no names and the addresses are made out in areas within areas. For example a proper address in Japan is somehow in the fashion of Russian dolls, starting with the name for the largest area container the prefecture or ken, to or fu, followed by the next smaller area nest, the name of the city or shi, again followed by the name of a smaller sized urban ward or ku, ending with the name of the neighbourhood, the cho or machi with a house number attached to it. This number has no intelligible link to a particular location along an anyway nameless street it is situated in: it is an official number of land registration.

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Figure 2.2 Ken system Source: Jinnai, 1984

Figure 2.3 Arial view of the Ken landscape with some urbanization Source: Fransje Hooimeijer

2.1.4 Water as self evident element of urban space Even thought it does not appear on the surface, the Japanese do prefer to arrange their cities according to a clearly defined – if not necessarily visible – structure of meaning (Jinnai, 1984, 137). Urban vistas became intimately bound with large scale features of the terrain, such as the shapes of mountains, hills and rivers. The many natural spots, waterside, cliffs and stretches of greenery remained within the cities; it never occurred to anyone to expend human effort on remaking them. On the contrary, such spots became favourite subjects for artists precisely because of their naturalness (Jinnai, 1984, 135).


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Figure 2.4 Water as self evident element of urban space in Kanazawa Source: Fransje Hooimeijer

An important meaning described in the former paragraph is the topographical situation of paddy fields. These form part of the Japanese urban framework. Lack of urban planning and focus on only the development of a Tan made the water system of ditches and little canals a self evident element of urban space. In many cities these are like arteries of the urban fabric, in front of houses with many little bridges, making garden separations, part of shrine gardens or later on city parks. Because of this almost natural way the water system has been a part of the scarce public space, it formed either the most important element of urban space or it was public space in itself. It is interesting to see how the contradiction between the private ownership steered urban growth and the public tasks of water management are interacting. The main focus of this chapter is the relationship between urbanization and water management in historical perspective. Per era this relationship will be studied and compared to the Dutch situation.

2.2 EDO, BIRTH OF A WATER CITY 1547–1657 2.2.1 Castle cities The base of the Japanese city is the castle town. There were many different castle towns, such as post towns along the trunk highways and port towns, market towns

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and religious centres (Sorensen, 2002, 13). The shogun situated the castle towns in strategic places and put a daimyo (a high samurai) in charge. – Before the Tokugawa period started a feudal lord Ota Do-kan chose a rather unpromising site in the Kanto region, beside the Tokyo Bay, where there was only a little flat land between the low hills of the Musashino plain and the marshy shore of the bay. The village was named after the family who lived there for centuries: Edo (Sorensen, 2002, 16). Till 1603 Kyoto was the capital but with the change of government this village Edo was chosen as capital and rebuild into a caste town. The guiding principle of city formation in high-city Edo can be understood to be of a balance between the will to plan that is common to all castle towns and the adaptation to the original topography that is characteristic of the Musashino uplands (Jinnai, 1984, 18). The people of the city, perceived the existence of the spirits of the land as the characteristics of ‘place’. That is why they always strove to create an environment imbued with the personality of ‘place’. Like in the Netherlands the personality of ‘place’, the characteristic of the territory, is called the ‘water wolf’, referring to the dangers of the wet situation of the territory. Besides the topographical situation the structure of the society was also instrumental in determining the layout of cities. Japanese society was made out in four main classes, each hereditary: samurai (warriors), peasants, artisans and merchants. Although the peasants were the poorest class, they were regarded as morally superior to the merchants and the artisans because they tended the land and produced the staple rice. Artisans produced goods for the samurai; merchants produced nothing and that made them consequently the lowest class (Sorensen, 2002, 13). Urban growth in the seventeenth century was stimulated by the move of the samurai to the castle towns and establishing these towns as home for the salaried administrative class, paid in rice (Sorensen, 2002, 14). The elevated castle, constructed on the principles of control and defence, would be the home of the daimyo and surrounding the castle the samurai had their quarters. The commoners would live outside in surrounding districts. The urban space was used to divide society in status groups. The distance of the samurai’s house to the castle would be the expression of his status in the hierarchy. The central keep was fortified; no attempt was made to surround the settlement with walls. The outer commoner districts, the temples and samurai areas were considered as part of the castle defence, not as something to defend. This is a typical spatial expression of the people being there for the state, not the other way around. The commoner districts were situated in the low-city and formed a ‘city of water’ built along the canals on reclaimed delta land, while the warrior areas of the high city created a ‘city of greenery’ among the rich hills and valleys (Jinnai, 1984, 68). The residential area for middle- and lower-class warriors developed especially early on top of the comparatively level hills to the west of the castle. The differences in height were used to make the backsides of the lots and just like in the Netherlands the tax was calculated over the width of the lot. In the Netherlands it was not the height differences but the water structures that were determent for the organisation of the lots (Jinnai, 1984, 17). In the high and low city each district was surrounded by internal walls, moats of rivers for defence and control reasons. The bridges over the moats and rivers were kept narrow to allow greater control over movement (Sorensen, 2002, 23). This topographical and social input on the design of cities makes Japanese urbanism quite distinct from European cities where distinct centres started centripetal structures.


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Figure 2.5 Backsides of the lots Source: Jinnai, 1984

The ‘different’ centres in Edo produced an eccentric urban structure that still forms the urban vitality of Tokyo today. 2.2.2 Claiming from water The low-city was not built in a totally unaltered natural setting, but made possible by diverting dangerous rivers like Tone River to the eastern seaboard (this is described in greater detail in chapter 3 and 5). The technology of diverting rivers and preparing a wet site for building was advanced step by step with the refashioning of nature, as engineering projects were instituted one after another at the beginning the Tokugawa period (1600–1868). It was clearly not chance growth, as Burke describes about the Dutch water towns, but the clear creation of the human will (Burke, 1959). Although the low-city is an altering of the natural setting, the urban arrangement that took shape paid close attention to detail, followed the original topography, and coexisted with nature. Its constructions displayed none of the extravagance of today’s technology that has drifted away from nature. The setting for the development of the low-city was between the Musashino plateau and the Shimofusa plateau (toward Chiba). The water system of the Tonegawa and the Arakawa rivers, which flow into Tokyo Bay, formed a floodplain. River Tone was diverted, part of Edo harbour was reclaimed, a planned network of canals and waterways was dug and district divisions were established to form the centre of the watery capital. The low-city has always lived in balance with the danger of flooding, and also later many alterations have been made to the river systems to make it safer. The main artery of the Edo water system, the Nihonbashi River, does not follow its natural course but rather is thought to have been created when Ota Do-tan (1432–1486) re-channelled the former Hirakawa River in the direction of Nihonbashi. During the Edo period when Tokugawa shogun was preparing to refit Edo Castle, he ordered the digging of Do-sanbori Canal as a waterway that would allow salt and other provisions to be transported to the area directly beneath the castle. Finally, in order to protect the reclaimed land of Nihonbashi district from floods, the Kandagawa River channel was opened and the southwest flowing Hirakawa and Koishikawa rivers were diverted east to empty into the Sumida (Jinnai, 1984, 70). Engineering of this kind put an end to floods on the

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Figure 2.6 Map of Tokyo around the year 1900 with one million inhabitants the largest in the world Source: Arie Graafland

lower reaches of the Hirakawa River and prevented the submersion of the port of Edo. It also put the earth taken from the Kandayama hillside to use in reclaiming the Hibiya inlet and creating city streets through the area. Although a number of natural rivers in the Edo lowlands were diverted, the result was an organic network of canals fundamentally in accord with the original topography. The moats that were dug around the outer castle works also obeyed the demands


Figure 2.7 Tokyo 1590–1603 Source: www.mid-tokyo.com



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of the Musashino highlands varied topography, with their interlaced hills and valleys. Human effort was added to nature. The serene appearance of this space composed of water, embankments, and greenery became a significant window of retreat from the surrounding city. Modern Tokyo inherited the cityscapes around the inner moat of the imperial palace virtually without change. The development of Edo combined the unique character of Tokugawa castle-town planning and the time-honoured practice of reading natural conditions in urban settings. From this combination emerged the beauty of the city, with its clear sense of order and its richness of variety (Jinnai, 1984, 71). 2.2.3 Low-city: Shitamachi In 1603, the Kandadai heights were levelled and the earth used to landfill the off-coast shallows and tidal flats from present-day Hamacho south to the Shimbashi area. With this, the downtown area, then centred around Dosenbori, spread toward Nihonbashi. The level areas of the low-city constituted a planned, checker-board-style urban organization of sixty-ken (360 foot) square unites typical of the ancient jo-bo- land division system (Jinnai, 1984, 16). In cities based on the ancient jo-bo- system, such as Kyoto and Nara, the divisions followed two principles – first, of coordinating north-south and east-west axes; and second, of a correspondence with four gods, as elaborated in ying-yang precepts. But in Edo, despite its grid-shaped divisions, the low-city deviated widely from both the north-south and the east-west axis. One possible explanation may lie in the original topography of the land on which the caste town of Edo was constructed as described above. The grid in the low-city is in perfect alignment with the canals suggesting that the first principle in Edo’s urban planning was to accommodate the lay of the land (Jinnai, 1984, 120). The canals of the low-city formed a number of island-like divisions. These islands call to mind the city of Venice, where the spatial autonomy of each island creates a single unit, both for livelihood and for human relations (Jinnai, 1984, 122). The islands of low-city Edo were similar. Even though the city’s space was planned according to a grid pattern, it was not simply a monotonous continuation of uniform units; instead, space was apportioned island by island, each with a personality of its own (Jinnai, 1984, 123). The Sumida, sweeping through the low-city and giving sustenance to the settlements throughout the river basis, is truly the counterpart of the Grand Canal, which runs through the heart of Venice. The canals that reach into every corner of the low-city resemble the water ways that course among Venice’s many islands. 2.2.4 Comparison with Dutch water cities The great difference between Japan and the Netherlands is of course the Japanese rainy season in May and June and the typhoon season in August and September. The Netherlands has no such extreme seasonal storms, even though with the change of the climate heavy rainstorms occur more often. Also most of Japan is above sea level, while the economic successful part of the Netherlands, by reason of the water, is situated in the lower western side. Here in the Netherland, the dynamics of the regional water system, which include groundwater and rainwater in combination with surface water, are crucial for the process of development and urbanization of the Dutch polders. The period from 1500 to 1700 was very significant for the development of water management and the transition from a feudal society to a republic in the Netherlands.


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From 1500 a new attitude, the offensive attitude, towards the water came about due to the fact that by the use of dikes and mills more control was gained. This happened after a period of accepting the wet circumstances till the year 1000 and defending against the water from 1000–1500. In the phase of acceptance the inhabitants were subjected to the forces of water and wind and lived on higher grounds: they simply accepted the situation as it was. All settlements were started on natural built up heights, for the same reason the choice for the political and economical centre of Edo was on the Musashino plain. In spatial set up the high kernel of the caste towns is very closely related to the Dutch cities. The defensive phase started around 1000 A.D. Measures of defence against the water were taken which were the most important condition for the creation of cities. The most conceptually interesting type of city is the dam city, like Amsterdam or Rotterdam, because of their tectonics: the integration between economics, technology, and beauty. The first generation of large-scale dike rings was built in the thirteenth and fourteenth centuries. On the location where a dike crossed the watercourse, a dam was built. Apart from this dam function, the dam ensured discharge of the river water into open water by means of a drainage sluice. Together with tidal movements, drain water was used in a practical way in order to ensure the depth of the harbour as well as city access for sea-going vessels. The drainage sluice could support only smaller ships, so goods from larger vessels had to be hauled or sold on the dam. The dam turned into a trading market, and the estuary outside the dikes of the peat river became a sheltered harbour. The dam city and polder become hydraulically as well as economically connected. Besides the dikes, the raising of grounds to drain and strengthen wet and weak soils and foundations under buildings were all demands that needed to be met to enable urbanity. The offensive phase marks the change from guilds to a more organized approach toward building up a body of knowledge. The other important transformation, from a feudal society to a republic, was strongly connected to this. The erection of the ‘Republic of Seven United Netherlands’ in 1579 meant the installation of an organized army where first knowledge build-up was done in building fortifications, canals, bridges, surveying, etc. In this way the military engineers became experienced in dealing with building fortifications and building on the wet and weak grounds of the Dutch territory. The grachtengordel (ring of canals) in Amsterdam (built in around the 1620s) is an integral design of land restructuring, surveying, and water management joined through the cooperation of the merchants for whom the city expansion was built – the city carpenter Hendrik Jackobzn Staets and the surveyor Lucas Jansz. Sinck, who drew up the plans. Amsterdam did not try to follow the idealistic view of a capitalistic city as other European cities did, but implemented this design as a blueprint of social and economic life, making use of the experience with building on the wet territory and the technological possibilities (Wagenaar, 1993, 9–12). The way the Japanese and the Dutch dealt with the topography of their territory and used it to make it productive or usable for settlement is highly comparable. Even the way the taxes were calculated based on the width of a lot connected to a public facility (street or waterway) are the same. In both countries reclaiming land from water started in a very early age and in both cases these areas were occupied by the lower classes. In Japan the defensive tool was firstly flood-way making, whilst in the Netherlands drainage and diking (polders) were the main tools. A great difference is that in Japan the shogun

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Figure 2.10 Burcht town Leiden Source: Burke, 1959

Figure 2.11 Caste city Edo Source: Jinnai, 1984


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Figure 2.12 Entrance to the caste of Edo,Tokyo today Source: Fransje Hooimeijer

dominated the social structure while in the Netherlands there was a great sense of equality, because one needed the other in the fight against water which led to the earliest form of government in the world: the water boards.

2.3 EDO, DEVELOPMENT OF A WATER CITY (1657–1868) 2.3.1 Meireki Fire The first month of 1657 marked a turning point in Edo’s history: fires broke out one after another, starting on new year’s night. The first of the fires collectively known as the Meireki Fire began at Honmyoji Temple in Hongo on the 18th January. Fanned by strong winds, the fire engulfed Hongo, Yushima, Surugadai, Hatchobori, Ishikawajima, Tsukudajima, Asakusa, Kyobashi, and Fukagawa. A second fire broke out in Koishikawa the following day, consuming Iidamachi, Kanda, the military class residences inside Tokiwabashi and Kajibashi gates, and much of Edo Castle. The Meireki Fire ravaged 60% of Edo and claimed over 100,000 victims. Ietsuna, the fourth shogun, believed that the absence of maps of Edo were a reason that the Meireki Fire claimed so many lives. Immediately after the fire, the shogunate initiated the production of maps of the entire city based on Western-style surveying techniques that were revolutionary in quality compared to the military maps that had been produced up to that point. These maps included previously unmeasured outlying areas, and were appropriately termed oezu, or ‘great maps.’ The Five Kanbun Maps were drawn from such survey maps and newly measured data.

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2.3.2 The multifunctional water front The low-city was the site of commoner economic activity, having developed initially during the medieval period because of the trade and commerce in and around the port of Edo. The waterfronts were in rudimentary condition, with no stonework along the water’s edge. But with the expansion of commercial activity in Edo and the establishment of its distribution systems, the waterbanks improved and began to take in a distinctive configuration (Jinnai, 1984, 75). The development of waterfront areas gave first priority to commerce and the distribution of goods. Warehouses became separate from shops and residences. Along the waterfront, which largely determined the city shape, a unique spatial configuration took shape, formed by the lines of rhythmical, linked warehouses with their white plaster and black tiled walls (Jinnai, 1984, 75). Outside the low-city into the suburbs, the water’s edge is no longer shored up by stone walls, but rather by wooden posts or natural embankment; many locations are also lined with cherry trees. The areas along the canals and rivers exhibit conventionalized ways of producing waterscapes, which are in full accord with their function and mode of use. Waterfront vistas truly provide a barometer for measuring the urban activities, from trade and distribution to recreation, proper to each area (Jinnai, 1984, 76). 2.3.3 Water supply Edo was composed of a plateau known as the Yamanote, and low-lying marshlands which were land filled to create a residential area. Landfill alone, unfortunately, did not provide a habitable environment: potable water could not be drawn from the ground, so waterworks had to be built. A dam was built at Koishikawa to divide the Edo (Kanda) River (drawn from the Inogashira spring), and extend it down to Kanda-ogawamachi. The construction work was assigned to Ieyasu’s retainer, Okubo Togoro, who was named ‘mondo (water chief)’ for his meritorious work. Other waterworks projects included the Akasaka waterworks, which supplied water from Akasaka-Tameike, and the Tamagawa waterworks, added later to cope with the increased population. 2.3.4 The bridge as significant urban element In looking at waterfronts, it is the location of markets that seems to be the most worthy of attention. Fish markets also developed very early along the convenient waterfront at Nihonbashi Bridge. In contract Nihonbashi Bridge provided a location where the shogunal government and the city’s residents could communicate their wishes to each other; there they could engage in a dialogue without having to appear in each other’s presence. The character of this public square was quite different from those of medieval Europe, which functioned as symbols of municipal self-government (Jinnai, 1984, 78). In both cases – in the republican city and the shogunal city – the apparatus of authority was incorporated into the central square so that the population could be kept under control within the stable routine of everyday life. The urban activities that developed in and around the waterfront markets are best illustrated by the square at the foot of Edobashi Bridge. After the great Meireki Fire, a


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Figure 2.13 Oezu, or ‘great maps’: the Five Kanbun Maps were drawn from such survey maps and newly measured data Source: Yonemoto, 2000

wide avenue (hiroko-ji) was laid out here as a firebreak (Jinnai, 1984, 80). The avenue located at the edge of the broad canal and filled with foot traffic moving on and off the bridge, naturally took on the bustle of a market, gradually acquiring the character of a popular amusement centre as well (Jinnai, 1984, 81). It developed into a public square that continued into modern times: particularly in the early years of the twentieth century, they presented viewers with splendid cityscapes composed of modern buildings set against great bridges. Today the cumbrous structure of the highway looms over the canal structure (Jinnai, 1984, 82).

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Figure 2.14 Waterfronts Source: Fransje Hooimeijer

2.3.5 Religious places Three reasons circulate for the building of shrines outside the city: first because of spiritual reasons described below in the case of Edo, second because of the danger of fire and third because of the power of the religion. In the year 794 Kyoto became capital and the shogun did not want to risk the Buddhists becoming too powerful. That is why the shrines were built outside the city. The roads to these shrines were filled with shops and markets and the shrines became separate centres outside the city. Still these centres are evident in Tokyo, for example Shibuya, Roppongi, Shinjuku etc. In the Edo high-city, temples and shrines were located at the edges of hills, set against a background of luxuriant woodland. In the low-city, all of the major temples and shrines were erected on sites that jutted toward the water’s edge, with the broad expanse of water providing a backdrop. The location of Edo’s religious spaces in the hills in the high city or along the water in the low-city was because mountains and water possess a sacred character owing to their connection with the spirits (Jinnai, 1984, 88). This method of situating religious facilities is diametrically opposite to the one used in European cities. In Europe, the cathedral – the religious centre of the city as a whole – was placed imposingly at the head of the public square. With the development of the modern


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Figure 2.15 Watersupply Tokyo Source: www.mid-tokyo.com

state, urban space came under official control, and these sanctuaries from the obligations of city life, with their vulgar energies so typical of Edo, were lost forever (Jinnai, 1984, 93). 2.3.6 Theatre, entertainment and leisure From time to time the Edo citizens were able to escape their enclosed, tightly administrated communities and relax in an anarchic area that they entered as free individuals. In Edo these areas were located along the upper reaches of the Sumida River, also due to the fact that water was connected to the spiritual world (Jinnai, 1984, 99). This fundamental tie was recognizably present during the early Tokugawa period. An analysis by Matsuda Osamu of illustrations depicting the various entertainments found in Edo’s brothels reveals their essential components – water, boat, and brothel – leading him to suggest that this combination expresses, in early modern form, the traditional Japanese sense of a spiritual world. This structure of a spiritual world was incorporated directly into the depiction of the Nakabashi theatre district (Jinnai, 1984, 94). The Sumida River, which had formerly flowed outside the city, was gradually being incorporated inside the boundaries of the city. For the residents of what had grown to be the biggest city in the world, the shady banks and broad waterside panoramas along the Sumida afforded an ideal setting for escape from the confines of daily life.

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Figure 2.16 The bridge as significant urban element Source: Jinbunsya, 2006

The government sought to provide an outlet for popular energies. It began to build temples and shrines and to plant pine and cherry trees in places away from the buildup areas, hoping to draw the populace there for recreation. 2.3.7 Comparison with Dutch water cities During this period in the Netherlands the offensive attitude further developed (Hooimeijer, 2006). The seventeenth century was a Golden Age for the Republic, when cities flourished through the economic growth, and the period wherein polder expansions were built. The cities stepped off their ‘dry core’ and, under ‘strict control,’ raised and drained their expansions. The ‘strict control’ was the result of the cautiousness with which an expansion of the polder city needed to be realized. First, the size of the expansion was determined, which did not only need to comply with the requirements of that time, but for centuries to come as well. A technical plan as a second aspect


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Figure 2.17 Tokyo (on the right), and other castle cities like Osaka, has just like Dutch polder cities a high centre and low lying expansions Source: Fransje Hooimeijer

was required to ensure that water could be discharged and controlled, and the water in the city canals would maintain a constant level. In most cases the start was initiated by building an encircling canal which was connected through the expansion area by means of a sequence of parallel canals. By means of sluices and windmills the water level of the canal system was regulated and the excess water discharged (Burke, 1959). Subsequently the reclaimed land needed to be raised in order to obtain the required protection level, and it had to be consolidated and prepared for building. Mud excavated from the canals was used for raising the level, and it was supplemented by ground. To stabilize the housing long foundation piles were driven in the ground in the deep-set stratum (of sand). It is superfluous to observe that in the case of polder cities random development is absolutely out of the question when land has been reclaimed, raised, drained and protected with so much effort. In polder cities one cannot speak of so-called ‘chance growth’ and due to the costs and efforts of building the reclaimed area an optimal use was demanded. The relation between the low-city and the high-city in the Netherlands is also very comparable to Tokyo’s set up. The consciousness of the characteristics of the territory and the way to make it liveable and productive for society are the same. The realization of the low-city of Tokyo has taken the same kind of effort, creativity and knowledge of the characteristics of the territory as in building the polder expansions in the Netherlands.

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The steam engine changed hydraulic technology and the urban landscape halfway through the nineteenth century. It became easier to control the water, making it do things it would not naturally do: i.e., to manipulate it. The spatial organization of the cities in the nineteenth century characterizes itself by the separation of conflicting functions and the bundling of functions that belong together (Van der Woud, 1987). Through professionalized technicians, urban design increasingly obtained a more technical instead of administrative basis. The ideas about urban design were made to be of secondary importance, incorporated by urban engineering, and degenerated into a technical profession within the municipal Department of Public Works. The first issues on the scale of the urban design were the introduction of the railway (1837) and hygiene issues of cities (e.g., water, housing) (Van der Woud, 1987, 377). After the completion of the grachtengordel and partially due to a period of architectural silence (1700–1850), no further large-scale city expansions were realized. The first planned expansion of Rotterdam after 1850 managed to reach the conceptual calibre of the Ideal City and the grachtengordel. City architect and military engineer W.N. Rose (1801–1877) designed an urban water system independent from the polder water system, referred to as the Water Project, assisted by landscape architects J.D. Zocher and L.P. Zocher. The plan served four purposes: flushing of the city water, lowering the groundwater level so that the polder expansion could be built, building a city walk, and the development of a residential area for wealthy citizens (Hooimeijer and Kamphuis, 2001). The plan is a perfect example of how water management, the structure of ditches and dikes, determined the layout of the expansion. At the end of the nineteenth century the Japanese studied the Dutch waterworks and invited the Dutch engineers to work on the Japanese rivers. Due to the fact that their country is not under sea level it was not necessary for extra measures to be taken to allow for urbanity.

2.4 TOKYO MODERN WATER CITY (1868–1945) 2.4.1 Meiji 1868–1912 The Meiji period (1868–1912) was a period of enormous change in Japan, which transformed itself from a closed late-feudal society to a modernizing state integrated in world economics and politics. Meiji is the transition from the Bakufu government to imperial rule, from late feudal to modern (Sorensen, 2002, 45–47). The change was forced in reaction to the neighbouring countries taken as colonies by the western nations. To ensure independency the Japanese saw the necessity to modernize, and went on a world tour to study the newest developments. From England they took the train knowledge, from Germany medicine and from the Netherlands water management knowledge. In Japan the central power left the local governments very weak and penniless. In the Meiji period the main focus was on the capital Tokyo and all measures taken there were transported to the other cities. Priorities were fireproofing and improving traffic arteries and the water supply. Even in Europe urban planning only became defined in the second half of the nineteenth century. The forces were: imposing planning constraints and building standards to landowners, regulating urban growth, zoning, building for the poor and planning frame works.


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First in England and then later in the Netherlands legal tools were developed in the last decades of the nineteenth century to regulate interventions in private interests concerning property by the collective in the interest of the public. In the industrializing cities planning was used to bring order. Disorder would bring disease, social conflict, and moral and political disorder. Improving the physical environment by urban planning (and spatial determinism) would also affect the social environment (Sorensen, 2002, 86). Non profit organizations like sanitary groups were defending the rights of the public to good housing and light and air in the cities. In the first half of the twentieth century the following questions came up: who has to pay for the public goods, how to ensure that the cheap housing is solely for the poor, how to compensate reduction of land prices and how to recoup for the public purse for the increase of land value by facilities. These financial issues were at the core of the proposal made by Ebenezer Howard whereby quality housing could be provided cheaply because of land purchase at low rural values and long term increases were retained by the community to pay for its social welfare. Two factors were key to different outcomes in Japan: the highly centralized system of government created during the Meiji period, and the relatively weak development of the middle class and the civic society (Sorensen, 2002, 88). Problems in Japan at the end of the nineteenth century were almost the same as today: the need to adapt built up areas to current needs, a lack of resources, resistance of landowners and local communities and the weakness of local government in relation to the central government (Sorensen, 2002, 46). The first large task was the restoration of Tokyo after the fire of 26 February 1872 that destroyed the Ginza area, the commercial centre of Tokyo. The ambition was to restore it with fire-resistant impressive buildings suitable for the imperial capital. Six days after the fire the new plan with significant street widening and requirements for buildings to be fireproof brick or stone was published (Sorensen, 2002, 61). The civilized look (western style) was attempted by widening the street, paved with stone and separate pedestrian sidewalks. Also the buildings had to be dimensioned according to the street width, and were built in brick: Ginza Brick Town (Sorensen, 2002, 62). Japan’s first city planning law was the Tokyo City Improvement Ordinance (TCIO) in 1888. It was exclusively concerned with the improvement of the existing built up area in Osaka, Kyoto, Yokohama, Kobe, Nagoya and Tokyo (the Pacific Belt) not with planning urban growth. It designated an overall framework for urban redevelopment that was not binding for private developers. Its contents covered roads, rivers, bridges, railroads, public parks, markets, crematoriums, and graveyards. In 1890 water works planning was added. However, revenue problems were encountered and the city ward improvement project was greatly delayed. Thus a City Ward Improvement New Design was announced in 1903 based on a selection of the minimum items for improvement. (1) Water Works The initial city ward improvement project made the provision of modern water works for Tokyo a priority in order to deal with the repeated occurrence of fires and the prevalence of communicable diseases. Work on the First Water Works Improvement Project began in 1891 and was completed in 1899.

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(2) Road Construction After the opening of urban railways in 1903, the need for provision of roads under the city ward improvement project was recognized. 123 roads with an extension of about 175 kilometres were planned, and had been largely completed by 1918. However, urban railways (streetcars) were laid out on almost all of these. (3) Urban Area Development Development of the Marunouchi district proceeded as part of the city ward improvement project. This included the building of roads near the moat around the Imperial Palace and the development of Hibiya Park. A western-style office district was built that was called ‘Little London,’ and Tokyo Station was opened in 1914. 2.4.2 Taisho- 1912–1926 The Taisho- period 1912–1926 started after the death of the emperor Meiji and the accession of Emperor Taisho-. Japan emerged as an industrial nation during this period with a doubling of GNP from 1910–1930 and a quadrupling of real output of mining and manufacturing, and of employment in heavy and chemical industries (Sorensen, 2002, 92). The Meiji Constitutions (1889) strongly reinforced the strong concept of landownership. The right to hold property was inviolable. Rapid urban and industrial growth, bad living conditions for the working class, social strife and spreading labour movement, democratization and pluralism in a political sense offered conditions for modern city planning during the Taisho- period. Urban planning was centrally organized in the Ministry of the Interior (Naimusho-) with the focus on economic growth by infrastructure (rail and highway) and cheap industrial sites in landfills, and ignoring urban quality (parks, sewer systems and local roads). Planning had a very narrow political support in an underdeveloped civil society. To enforce a stronger planning system the political support was needed and a technical development of the skills to enable it. Also some limitations should be set up for landowners in how to make use of their land (Sorensen, 2002, 90). State power also expanded and by 1930 there was little effective political space for urban and social improvement, the indication of essential fragility of democratic institutions in the Taisho- period. Also this power left no room for legal authority or financial independence of local even metropolitan governments (Sorensen, 2002, 97). On the basis of the TCIO the City Planning Law and Urban Building Law (1919) were the first national city planning framework. They stayed effective for 50 years and introduced land use zoning, building constraints and systems to plans. In anticipation of the laws the Ministry of the Interior gained a City Planning Section in 1918 but it took until the 1930s until the first textbook on new city planning and building regulations came out (Sorensen, 2002, 108). Draft City Planning Law included main provisions by TCIO: designating and building public facilities, zoning system, building line system and urban Land Readjustment. The Urban Building Law included building regulations use, height, lot coverage and a building line (Sorensen, 2002, 110). The new laws enforced the central state and weakened local governments even more. The 1919 law ordered that all plans needed to be approved by the Ministry of the Interior, local government had no legal powers. The problem was that the national


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legislation admitted no variation in zoning or building regulations between areas with quite different urban patterns and problems. All Tokyo’s problems were imposed on the whole country (Sorensen, 2002, 111). The centralization enabled high speed plan making, but there was no planning experience and the government had a preference for project control rather than general regulations. Furthermore there was no public interest or education and the local government remained responsible for sewer, side walls, roads, parks, childcare, libraries, and hygiene (Sorensen, 2002, 113).

2.4.3 The 1919 City Planning Law In detail the 1919 City Planning Law had the following aspects. 1) Land use zoning (residential, commercial, industrial); It did not bring a strict separation between the zones but only excluded functions. This was due to administrative complexities of the national government. Also three special areas were installed: scenic areas (natural parks) beautiful city (American City Beautiful Movement – manourchi) and fire prevention. 2) Urban Building Law; Rules about the allowable land use, building coverage and height (per zone). It had basically more control on building types than land use. 3) The building line system; This gave way to infrastructure. The problem was that the rural lanes (over 2.7 m wide) were automatically used as building lines and produced very narrow streets. 4) Facilities designation; The designation and building of public facilities was in many regards the main planning activity and like the TCIO roads, water and sewer systems in built up areas were considered as the most public. It affected more central power. 5) Land Readjustment (LR); Method of pooling ownership within a project area building urban facilities such as roads, parks, and dividing the land into urban lots. The method came from the agricultural scene to prevent scattered landownership and build irrigation. Landowners must put up to 30% of their land up for public use and two out of three of the owners must agree, then all the owners will be forced to comply. In Japan LR is the mother of town planning (Sorensen, 2002, 114). 2.4.4 Tokyo earthquake 1923 The urban space of Edo was designed for the flow of water and foot traffic (Jinnai, 1984, 126). First, as part of the effort to transform the pre-modern caste-town of Edo into a more functional, more modern capital, the many layers of box-shaped or curved streets gave way to a new road system that ensured the smooth flow of traffic between the inside and the outside of the city. The wooden gates partitioning one section from another were also torn down. During the mid-Meiji years major streets were both repaired and widened under an officially planned urban renewal project said to be inspired by Haussmann’s plans for Paris. These projects introduced a new sense of scale to Tokyo’s major avenues, radically altering the city’s appearance (Jinnai, 1984, 128). In 1923 a large earthquake destroyed 3,636 ha of Tokyo and the low-city for the most part. The Kanto Earthquake resulted in a total dead and missing about 143,000

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people and 104,000 injured. Approximately 128,000 structures were demolished by the shock and as many as 447,000 structures were lost in the fire. Tokyo lost 44% of built up area (366,000 houses) in the fire and 60,000 people were lost (2.4% of the population) (Matsuda, 1990, 111–112). In succession to the developments at the beginning of the century the space made by the earthquake was used to widen old narrow streets, lay out new ones, and to remove row houses and the rear alleys on which they stood. The Ministry of the Interior’s Reconstruction Bureau produced a number of posters emphasizing the unsanitary and dangerous conditions of the backstreets and arguing the urgency of street reorganization (Jinnai, 1984, 129). The reconstruction was the first large project of the 1919 Planning Act. A special Ad Hoc Town Planning Act was established that allowed LR in built up areas and the Reconstruction Board could work without the consent of landowners (no compensation was given for taken land). Almost 85% of the damaged area (and a total of 3,041 ha) was reconstructed with 65 LR constructions (Sorensen, 2002, 126). LR was profitable for landowners because the facilities were increasing the land value, they did, unsuccessfully, oppose to the 30% land they had to give up for these facilities (Sorensen, 2002, 128). It had a long term impact in the following ways: the LR technique developed further, city planning as a profession developed, organization of building public housing, boosting the public image of city planning and self image of the profession and a new aspect that was introduced that governments could initiate LR projects (Sorensen, 2002, 131). Also with the use of the Ad Hoc Town Planning Act 400 bridges were reconstructed in steel, side walks, previously unknown in Japanese cities, were built and a five layered hierarchy road system developed (Sorensen, 2002, 129). Neatly arranged city districts emerged, along with widened main streets and a radical reduction of the number of alleyways. The elimination of ‘interior’ spaces, however, forced the sights and the smells of everyday life, hitherto confined to the backstreets, out into the main avenues of the low-city. Laundry and potted plants lining the main streets came to define a uniquely low-city atmosphere. Thus, streets replanning resulted in the privatization, or ‘alley-ization,’ of the main streets. This privatized open space displayed the vibrant, living feelings of the low-city (Jinnai, 1984, 130). At the same time, the modern city continued to grow relentlessly, thriving on one ‘cruel’ remodelling plan after another. Whole city blocks were often covered by one huge building, leaving neither interstices nor space to the rear. Underground streets had come into being as a phenomenon peculiar to Japan, providing a clear functional division between the surface and the depths of the city (Jinnai, 1984, 131). A glance at the history of modern Japan makes it obvious that transplanting the European notions of artfully arranged squares and tree-lines streets directly onto Japanese soil has failed to create a space that is both interesting and full of energy. Rather, it is only disorderly, thriving and appropriately small spaces, where human feelings and not an expanding vista take charge, that one can find a properly Japanese urban life (Jinnai, 1984, 132). 2.4.5 Water management Tokyo suffers from three types of flood disaster: collapse of riverbanks (the three largest were in 1742, 1786, 1846), storm surges driven by typhoon (eight storms have


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Figure 2.18 Tokyo earthquake reconstruction Land Readjustment District #18 in down town Tokyo east of Tokyo station and bounded on three sides by canals.The upper shows landownership and road pattern before, and the black of the lower map show new areas of road space after the execution of the project Source: Sorensen, 2002

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Figure 2.19 Reroute of infrastructure after the earthquake Source: Sorensen, 2002

damaged the lowlands since 1910) and heavy rain storms (for example Kanogawa typhoon 1958 of 444,1 mm water flooded 211 km2 and 480,533 houses). A flood by earthquake could be the fourth one but that has never happened until now in the Tokyo lowlands (Matsuda, 1990, 113).


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During the Edo period (1603–1867) the original river was flourishing in river transport and had a lot of waterfront markets. The Meiji period (1868–1912) and the first River Law (1896) brought centralization in river control. At the same time the introduction of transport by rail brought decline in the transport over water (Arakawa-Karyu River Office, 2004, 18). Also at the beginning of the twentieth century the Arakawa floodway was built, a great example of a flood protection measure that was an important condition for urbanization. Chapters three, four and five will elaborate about these river measures in great detail. Water management has been the structuring force in low-city as described above. However, in response to a massive flood in 1910 again counter measures were necessary. The 1910 flood was caused by rainstorm of 1.210 mm in Naguri, Saitama prefecture. The river overflowed and killed 369 people and destroyed 1,679 homes, flooded 270,000 homes and affected in the end 1.5 million people (Arakawa-Karyu River Office, 2004, 24). To prevent this from ever happening again the Arakawa flood channel was excavated and is now called the Arakawa River, the old course is Sumida River (Arakawa-Karyu River Office, 2004, 4). 2.4.6 Transformation of a water city The history of Tokyo since the Meiji Restoration is the history of its transformation from a city on water to a city on land. It is possible to follow the path of urban change by using water as a guide. In reading the formation of Tokyo as a modern city, water does, indeed, serve as an effective keyword (Jinnai, 1984, 107). The spatial structure of Edo’s waterfront with its merchants’ houses, public thoroughfares, warehouses, and canals – all visible from land facing the water – was carried over into the Meiji period and many areas retained this form until the 1923 earthquake. After the 1923 earthquake the water fronts were proudly rebuilt with western architecture and appreciated in a western way, and were western to look at (Jinnai, 2004, 58). The mortar warehouses no longer conveyed a feeling of Edo to the modern city. But water transport was still brick, concrete warehouses were still built along the canals, and a number of the old brick or stone warehouses remained standing (Jinnai, 1984, 76). Although certain canals whose shallowness made them ill-suited to transport were filled in, the general trend was towards expansion and improvement like new embankments for the Kandagawa River, and water buses offering the low-city a vital network of public transportation. Though the waterfront was deprived of the charm of Edo, water continued to exert considerable power over the urban environment (Jinnai, 1984, 174). Originally the water was a place for performance, to experience the delights of spiritual space and something that encompassed every aspect of human existence, boring intimate ties to cosmology. But in the 1920s, waterside space was re-imported to Japan by way of western cities and re-evaluated. It became an object to look at, as a central element in the formation of urban beauty. Thus waterside spaces in the post-earthquake Tokyo provided the most direct expression possible of modernism in urban place formation. Also the public space was modernised after 1923, for example the old bridges that had been destroyed in the earthquake were replaced by modern ones. Authentically modern urban space was first achieved somewhat further upstream on the Nihonbashi River, at the base of Nihonbashi Bridge. The original bridge was replaced in 1910 by a splendid stone structure with a flowing arch, designed by the

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architect Tsumaki Yorinaka. Nihonbashi led the way in this fundamental change in Tokyo’s urban space, which began in the 1910s and gave an unmistakable form to the city during the years of recovery from the great earthquake of 1923. Strong examples are the earthquake recovery projects of Hamacho- and Sumida parks, both featuring modern promenades along the Sumida riverfront. These projects and Kinshi Park were meant to promote the health, sanitation, rest, and recreation that Tokyo residents required. They were also planned to aid in fire prevention and to serve as evacuation sites in case of emergency (Jinnai, 1984, 175). Japanese civil engineers became self-sufficient in this period. Even though relying on Western precedents, they produced many bridges noted for their superbly individual design. Bridges had served since Edo times as a key accent in the vistas of the low-city and architects not only considered bridges’ as simple functional or structure, but also looked for designs with links to the environment of the region. These bridges still play an important role in shaping the cityscape of low-city of Tokyo (Jinnai, 1984, 177). The meaning of urban spaces like the bridges cannot be expected to change overnight, and indeed, most of the plaza-like spaces that appeared in post earthquake Tokyo were located at the foot of the city’s bridges. Transformed into regulated space, they may have lost the original plurality of meanings associated with the waterside, with its mixture of romantic nostalgia and raucous vulgarity. But these bridge side spaces offered the perfect setting for an urban design that would produce new kinds of urban beauty (Jinnai, 1984, 179). 2.4.7 Urban space Lot adjustments after the earthquake of 1923 led to the institution of systematic planning methods for streets and buildings. The 1920s architects and builders had grown proficient in the Western architectural techniques they had copied and studied since the late nineteenth century. One of the most noticeable results of Tokyo’s earthquake recovery programme was the planting of trees, lining the streets (Jinnai, 1984, 179). Before the Meiji period the low-city of Edo was divided according to a grid pattern, no street crossed the city diagonally. Diagonal composition itself was highly alien to Japanese architectural methods, which were based on vertical and horizontal axes (or wooden pillars and crossbeams). Moreover, because taxes were levied on the basis of lot widths facing the street, it was impractical to cut corners diagonally at crossroads. But conditions changed drastically during the Meiji period. The border gates were removed and streets were broadened, beginning with the major arteries. As pedestrians were replaced by rickshaws, horse cars, and eventually streetcars, the speed and the scale of traffic changed. Land taxes began to impose on the size, not the width of the lot, a development that freed corner lots for other uses. As a result, the significance of crossroads increased gradually within the urban space (Jinnai, 1984, 149). During the Meiji period the Western-style buildings stood conspicuously alone without any relation to the rows of traditional warehouse structures that surrounded them. When entire districts were modernized to create an urban context, buildings were consciously designed to interact with elements of exterior space such as streets and plazas (Jinnai, 1984, 186). The traditional Japanese cities characteristically combined two coexisting models of living: that of commoners, with its focus on ‘establishing a shop’, and that of the ruling


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warriors, with its desire to ‘establish a grand residence’. These two models were handed down without modification to Tokyo from the Meiji period (Jinnai, 1984, 161). Two different strands of spatial arrangement were drawn together in the process of situating newly created public offices and universities within the city: the traditional notion of ‘establishing a grand residence’ was applied to the overall design, while the Western concepts of axis and symmetry, which have something in common with the already familiar composition of temple and shrine architecture, were introduced only to the most public and ceremonial frontal space between gate and entrance (Jinnai, 1984, 168). These buildings acquired a self-completing form within an individual lot within the mosaic of Edo’s pre-existing urban context. The result was an eclectic cityscape that enthusiastically incorporated a new profile while keeping intact both the fundamental urban structure and the traditional notion of ‘establishing great residence’ (Jinnai, 1984, 169). 2.4.8 Transition: pre modern industrial and modern Tokyo’s transformation into a city on land was strongly enforced with the development of the railroad. But initially this was also in association with water. Edo’s internal transportation network was organized around the canals; land and water came together on the banks. As goods concentrated there, warehouses appeared and wholesalers gathered. Both people and goods oriented their movements towards the waterfront. In the early days of the railroad, every important station was built along the water, just in front of the canals at the edge of the old city. After the Restoration, the Meiji Government began to remove the theatres and waterside teahouses from the avenues alongside Ryo-goku and other bridges and replaced them with modern buildings representing modern state. The First National Bank at the base of Kaiunbashi Bridge was the first followed by commercial buildings in the area of Edobashi and Yoroibashi bridges. This area became Japan’s first business district representing the hearth of the Japanese economy and directly connected to the hub of the city’s water transportation system. All these developments in the build up cities contrasted sharply with the suburban land development that was more into making profit then nice designs. The market was growing but only those in the upper middle class could afford a house. Some ideas about Garden Cities were explored but the greatest long term impact of garden city projects was the creation of a strong link between suburban land development and the building of private railways (Sorensen, 2002, 141). The building of the railway was for a long time the urbanizing factor, in size and location. Few people had cars; only in the 1970s did the car provide competition for the railway (Sorensen, 2002, 142). Only in the 1950s did the organization of suburban development come up. After 1930 all state money went towards the expansion of the country. Until the end of World War II in 1945 there was no focus on interior state. The interwar period is characterized by the following trends: unplanned growth, intra urban transport and the beginning of planned suburban growth. The Japanese situation is characterized by the first seen small islands of planned development set against a background of haphazard sprawl and structured by large scale transportation systems (Sorensen, 2002, 146). The term sprawl in western countries is used for low density spreading of cities.

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The Japanese style of sprawl adds a few characteristics: very small developments of 1–10 houses, along the existing rural lanes, no road network improvement and no sewerage network (Sorensen, 2002, 206). 2.4.9 The Sho- wa (Enlightened Peace) 1926–1989: Early Sho- wa (1926–1945) During the era of the weak emperor Taisho- (1912–26), the political power shifted from the oligarchic clique (genro) to the parliament and the democratic parties. After the death of Taisho-, the first part of Emperor Sho-wa’s (Hirohito) reign (Early Sho-wa between 1926 and 1945) as sovereign took place against a background of increasing military power within the government, through both legal and extralegal means. The Imperial Japanese Army and Imperial Japanese Navy had held veto power over the formation of cabinets since 1900, and between 1921 and 1944 there were no fewer than 64 incidents of right-wing political violence. For 15 years the whole country was dedicated to war, starting with the conflict with the Chinese about Manchuria in 1931, the second Sino-Japanese War (1937–1945), the occupation of French Indochina (1940) and joining the Axis powers Germany and Italy started the war against the United States and Great Britain: the Allied Forces. The turning point in the Pacific War was the battle of Midway in June 1942. From then on, the Allied forces slowly won back the territories occupied by Japan. In 1944, intensive air raids started over Japan. In spring 1945, US forces invaded Okinawa in one of the war’s bloodiest battles. On July 27, 1945, the Allied powers requested Japan in the Potsdam Declaration to surrender unconditionally, or destruction would continue. However, the military did not consider surrendering under such terms, partially even after US military forces dropped two atomic bombs on Hiroshima and Nagasaki on August 6 and 9, and the Soviet Union entered the war against Japan on August 8. On August 14, however, the Emperor finally decided to surrender unconditionally. 2.4.10 Comparison with Dutch water cities The industrialization and urbanization also started in the Netherlands to take accelerating forms at the end of the nineteenth century. The big difference with the Japanese situation is that in reaction to the upcoming pressing issues a profession and practice of urban design came up. The combustion engine, electricity, and the development of the soil mechanics at the beginning of the twentieth century were the changing forces of the manipulative era (1890–1990). Besides the shifting sources of power (from steam to diesel, oil, gas, electricity) in the technology of draining, the hydraulic technology also changed. The scientific research in soil mechanics added to the development of better and more refined ways for building site preparation, and the enlargement of machines to move grounds made it possible to realize them. The control became absolute: manipulation. Hygiene problems, caused by the city’s water were slowly but surely of influence to the spatial effect of water management, due in part to the progressing development of the steam engine and later of the internal combustion engine. While the functional meaning of water increasingly devalues, ‘nature’ in the city gains proportional interest. Besides


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Figure 2.20 Comparison with Dutch water cities Plan Zuid Amsterdam Source: MaartenJan Hoekstra

traffic, buildings, and water, a new element in the city structure was introduced: public space. At the same time, structures of buildings, traffic and the combination of water and green spaces were separated. These structures coincide in traditional cities, such as in the Amsterdam grachtengordel, which has one single main structure containing all the elements. At the beginning of the twentieth century it appeared as if water and green spaces could only guarantee their right to space when they were combined. Plan Zuid was one of the first urban designs that combined the different aspects in an overall plan. A way of seeing the city in the Japanese situation was impossible due to the power of the landowners. In Plan Zuid (1915) the water structure is part of the green structure, and the green spaces acquired rights as a public area as an exponent of water. At first, the combined structures of water and green areas were of importance and formed the backbone of the city design in combination with the structure of traffic. The structure of public areas and water (which, can be sailed on as well in Amsterdam) follows a displaced shadow of the traffic structure. Later, as well as now, the urban composition became a derivative of the traffic structure and accessibility principles due to the importance of motor vehicle traffic. The impact the railway and the car have had on the urban structures has been great both in Japan and the Netherlands. The transformation of water to land cities started in both countries in the Meiji period and has been transforming the cities during the whole twentieth century, not only by starting to fill in the waterways but also by organizing urban growth and urban structure along the lines of the new mobility and not like the phases before using the rules of the topography of the territory.

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2.5 TOKYO THE DESTRUCTION OF A WATER CITY (1945–1973) 2.5.1 Mid Sho-wa (1945–1973) This ‘in between’ period during the ruling by Emperor Sho-wa began with the destruction of the water city. This can be connected directly to the destruction of Tokyo in the Second World War: the rubble of the bombed buildings was used to fill in small waters in the city (Jinnai, 2004, 59). Not only did the war not do the urban water system any good, urbanization was also killing it. The land use patterns, depending on the topographical characteristics, changed and the plains started to become denser every decade (Haruyama, 2005, 5). During the economic growth in the 1960s and 1970s many people from the countryside moved to the industrializing cities at the Pacific Belt Region. 2.5.2 Economic focus After more than 15 years of focus on war, to the middle of the 1960s all means and energy was put in the industrialization by a most powerful and autonomous central government providing, creating jobs and consumers (Sorensen, 2002, 178). All investments went into roads, ports, dams, power lines, land reclamations and railway in the Pacific Belt Region (from Fukuoka to Tokyo). This odd mix of communist planning control and capital ownership is characteristic of the rapid growth after the war (Sorensen, 2002, 179). The focus of planning on industrial infrastructure contributed largely to the economic growth. The budget of public works was in 1960 for 41% dedicated to roads, harbours and airports and only for 5,7% to housing and sewers. The latter was almost doubled in 1970 to 11,2% but also the budget for roads, harbours and airports rose to almost half of the total public works budget to 49,9%. Landfills were basically ‘given’ to industries and in contrast there was very little interest in long term patterns of growth, residential quality of life, social capital formation (parks, libraries, recreation) and the environment (Sorensen, 2002, 182). The war had fostered industrialization accompanied by an influx of population to the cities, along with the formation of the working class and the masses in general. These changes provided the background for the rise of a new, democratic way of thinking. In addition, economic growth brought about a boom in consumption, giving popularity to the word culture. The rapid advance of urbanization provoked all manner of urban pathologies: increased building density, the appearance of inferior housing areas, economic and housing distress among the city’s people, and speculation that accompanied the jump in land prices (Jinnai, 1984, 173). During the rapid industrialization and urbanization in 1950s and 1960s, countermeasures against heavy industrial pollution and disorderly urbanization were urgently needed. Based on polluter-pay-principle the eco-friendly products increasing and ecoindustries were enhanced to boost GNP finally to higher level than expected (Matsushita, 2007). 2.5.3 Modern Planning The Ministry of the Interior was reformed after the war in 1947 into three specialized ministries: Labour, Health and Welfare; Construction; and Local Autonomy Agency.


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After the war bureaucracy emerged as an even more powerful institution due to: the (forced) disbanding of the military, dismantling the political role of the Emperor and the weakening of the old conservative political parties. In the case of planning nothing really changed (Sorensen, 2002, 153). Significant functions of the pre-war period were the base of the post-war dramatic phase of Japanese urbanization (Sorensen, 2002, 171). Also, even though large parts of Tokyo’s built up area was destroyed, what remained were property ownership patterns (including public property in the form of streets, parks, canals and other infrastructure). These remain decisive in the rebuilding of the city (Sorensen, 2002, 167). Based on the Tokyo reconstruction after the 1923 earthquake the ambitious reconstruction of the WWII damage was set up: The Special Planning Act (1946). This act was altered in the following years by a basic policy for 10% space for parks and stronger planning control in 1945 (Sorensen, 2002, 159). In 1954 a new LR act, that is still in power till today, came into use. The new ruling added land lease holders to the decision makers, and local public cooperation could also take the initiative to the projects. It was primarily used for urban expansions in urban areas, for downtown redevelopment, new town building, public housing projects or railway and mass transit development. The national government could subsidize the local government who initiated the projects (Sorensen, 2002, 183). As before, national capital was allocated for productive sectors: urban development was focussed on infrastructure and always with landowners by skilfully sharing the benefits. Post-war rapid growth produced complex patterns like a wide range of land uses and haphazard un-serviced development, the main focus was placed in the widening of streets (Sorensen, 2002, 191). Housing was left to the private sectors (Sorensen 2002, 184). The housing policy resembled an emergency shelter programme for refugees rather than a careful city planning programme. In 1963 a New Town Act (Japan Housing Corporation) (Sorensen,

Figure 2.21 Early 1960s an enormous air and water pollution problem came up Source: Arakawa-Karyu River Office, 2004

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2002, 185) was set up but it in no way compared with the New Towns we know outside Japan. They were basically sleeping cities, no public facilities and very well situated next to public transport. The reason for this neglect was that Japan never experienced serious social problems associated with public housing estates, just as there was no vandalism and no personal safety issues (Sorensen, 2002, 187). The Urban Building Law was transformed in 1950 in the Building Standard Law, abolishing the building line system and introducing the Road Location Designation System that provided a minimum road width and no overall system, even though the name might suggest it (Sorensen, 2002, 197). Before the New City Planning Law of 1968 the orientation was on project planning and implementation of a highly centrally organized and extremely laissez faire government policy (Sorensen, 2002, 199). 2.5.4 Disappearing water city Modern city planning had no concern for the individual conditions of particular sites. In wilful ignorance of the underlying powers of place, land has been reclaimed and establishments erected that look absolutely the same wherever they occur. Venerable rivers and ponds have been filled in, and vegetation destroyed (Jinnai, 1984, 19). In the early 1960s an enormous air and water pollution problem came up. Many people became ill and even died from the pollution. The water in Tokyo smelled so bad that the people on boats could hardly breathe. Particularly in dense residential areas the problems were severe, due to weak zoning. The Ministry of Construction provided the sewer system in the 1960s and in 1970 only 16% of the population was connected. In 1988 this figure rose to 40% and in 1998 64,7% of households had a connection.

Figure 2.22 Gaikaku teibo: the construction of a high concrete wall or dike along the Sumida River and other canals in the 1960s Source: Fransje Hooimeijer


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The environmental conflict was the driving force behind the 1968 City Planning Law that was the changing force of the following period (Sorensen, 2002, 201). Not only in quality also in quantity had problems come up. In the 1960s groundwater extraction for drinking water caused heavy subsidence in the dense Pacific Belt Region concentration. After 1970 the transference to the urban areas decreased and shifted towards the outer fringe of the cities, taking the paddy fields (Haruyama, 2005, 6–7). Urban development changed hydrological conditions by deforestation, house building, road pavement, drainage works etc. New flood protections like separation levees, river enlargement, diversion channels and embankment heightening including watershed management were developed (Haruyama, 2005, 9). The transformation from paddy fields into cities brought the loss of inundation capacity; hence rainwater collected and was running into the river protected by artificial embankments causing flooding downstream. After 1978 the ‘Comprehensive storm and flood water control measures’ changed land cover and land use planning in watershed areas into environmental-based zoning and a land use plan (Haruyama, 2005, 3). Two important countermeasures for flood disasters in the Tokyo lowlands was the channelling of the Arakawa River and the so called gaikaku teibo: the construction of a high concrete wall or dike along the Sumida River and other canals in the 1960s (Matsuda, 1990, 113). Eventually it led to the complete destruction of the closeness between city and water. The surface of the water became invisible from the ground floor. Rivers and canals turned into muddy ditches, including the Sumida River that is assumed to have suffered from the worst water quality in 1964 (Jinnai, 2004, 60). The water gradually improved even to make fish return to the river around 1970 (Jinnai, 2004, 61). The greatest enemy of the urban water in Tokyo was the highway. At the end of the 1960 many highways were built in the rivers and canals. Some were even pumped out

Figure 2.23 Highway on water for the Olympic Games in 1964 Source: Fransje Hooimeijer

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and used as a highway, making use of the old bridges in the new traffic system. The incentive for this project was the Olympic Games in 1964. Since this was the comeback after the war (after decades of supervision by the Americans) of Japan as player on the world stage, and the first Asian Olympics, no expenses were spared: $3 billion dollars was spent to rebuild the city and to introduce a highway system. Because the grid shaped urban structure was not suitable for the motorways where cars could go fast, the soft curved lines arising from the rivers and canals were perfect for this aim. However, the motorway was not welcomed in all places; the construction over the Nihonbashi was strongly obstructed because of the symbolic meaning of the bridge. Nevertheless the motorway was built (Jinnai, 2004, 60). 2.5.5 Kenzo Tange’s plan for Tokyo (1960) At the same time the planning for a new city in the Bay of Tokyo also took shape as a part of the Plan for Tokyo by Kenzo Tange (1913–2005). The Japanese architect Kenzo Tange was a student of Le Corbusier, and one of the first modern architects in Japan. He played an important role in the post-war rebuilding of Japanese cities. In 1960 Tange published his monumental ‘Plan for Tokyo’ a stimulating theoretical exercise that foresaw a need for Tokyo to restructure into a twentieth-century city. According to the Japanese tradition it should be done in analogy with nature, ‘the various architectural works will form the leaves, and the transportation and communications facilities the trunk of a great tree’ Tange wrote. The plan envisaged a vast radial overlay of buildings and roadways above and beyond traditional Tokyo. It included massive manmade islands in the middle of Tokyo Bay, connected by bridges. According to the designers, this could have been done without interfering with the ecosystem of the bay, anticipating the coming planning developments, and the ship traffic.

Figure 2.24 Highway instead of water for the Olympic Games in 1964 Source: Fransje Hooimeijer


Figure 2.25 Kenzo Tange’s plan for Tokyo Source: Akira Inodomi

Figure 2.26 Van den Broek & Bakema for Pampus, 1965 Source: Netherlands Architecture Institute

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The reason for it not being realized is that it was not paying attention to basic requirements, it was an urban vision. Tokyo Bay has been very important to Japan and the moving of the port was one of the requirements of Tange’s plan that was not realistic. Even so, today the port is moving and living and working on new islands in the Tokyo Bay; Tange’s plan is realized today. 2.5.6 Comparison with Dutch water cities The Plan for Tokyo by Kenzo Tange is very comparable, in conception, design and most of all in not being realized, with the plan by Van den Broek & Bakema for Pampus (1965). Van den Broek & Bakema designed for the environment of Amsterdam, and proposed an alternative approach to urban and regional planning, breaking through the traditional separation of city and landscape. One of their proposals was to integrate water and city by turning the axis of urban development at the eastside of Amsterdam from a tangential position southeast – northwest to a radial position from west to east: Plan Pampus. The firm spine with the flexible system of modules is in both plans the basis of the design, the Dutch plan coming from the ideas of structuralism. This way of thinking was explored by the SAR (Foundation of Architectural Research) in the 1960s and also seen in the plan of New Babylon by Constant Nieuwenhuis. The key words of the second half of the twentieth century in the Netherlands were advanced technology, welfare state, and disintegration. Old religious, political, and moral values and certainties started to waver. Technology became more and more dominated by measurement and prognosis. Besides the boundaries drawn between the disciplines, the construction of the city and its structure fell apart in housing, infrastructure, and green areas. In the grachtengordel and the Water Project all these structures together orchestrated the city’s ensemble. Now the main structuring element was (car) mobility. The breaking up of the various structures illustrates the segregation between engineering and urban design (Van Eijk, 2002). The designers of the grachtengordel and the Water Project were engineers, and they developed their own vision of urban design. At the beginning of the twentieth century urban design became an autonomous discipline and the tasks were divided. Civil engineers solved the water issues in such a fashion that the urban designer never even knew that they had been dealt with. Technological progress, such as improved pumps and calculation methods, made the preparation of a larger site possible by raising it with sand. This meant that in combination with an underground drainage system, significantly less surface water was needed. In the end the urban designer considered water a waste product, to be situated on the outskirts of districts or integrated into the infrastructure or the green space system. The water system as designed by civil engineers cannot be recognized as such, since underground pipelines alternate with the surface water. Moreover, the sand package provides urban designers with a tabula rasa on which each required urban design can be realized without any concern for the water system. Where in cities up until 1940 the total surface of the city contained 12%–15% water, in post-war city expansions, this percentage was often reduced to less than 5%. Amsterdam’s western garden towns resulted from the pre-war General Expansion Plan (AUP) for Amsterdam produced by Cornelis van Eesteren. Van Eesteren advocated a transparent city, in which wedges of landscape would both penetrate and blend


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Figure 2.27 Western part of the General Expansion Plan for Amsterdam by C. van Eesteren (1934) Source: Municipal Archive Amsterdam

with the city through a continuous fabric of green fields and apartment buildings. The careful orchestration of the various urban functions (housing, working, recreation and traffic) and the open and spacious layout has made the AUP into the icon of modernist urban design. It is the ideal of a pure, healthy, open and transparently ordered city, created through extensive urban survey. Regarding water management, Van Eesteren conducted one such survey on the necessary and available quantity of sand. Amsterdam had been traditionally raised to

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Figure 2.28 Osdorp Source: Municipal Archive Amsterdam

outlet water level, and Van Eesteren had no intention of breaking with this tradition: ‘The arrangement of the system of waterways, the water storage area, the system of sluices and pumping, are all controlled through the level achieved by raising. A city built as an outlet waterway town has to be developed in an entirely different way from a polder town’ (Van Eesteren, 1934, 159). Because: ‘an urban expansion executed in this way [as a polder town] would have to be laid out to suit the pumping, one consequence of which would be a need to reserve a considerable surface area of the city for canals and watercourses to arrange for sufficient water storage’ (Van Eesteren, 1934, 25). The lower polder town would have to be connected to an old city at outlet water level. Van Eesteren saw the connection of the road and water systems as particular design issues. The through roads would have to be linked by slopes, the canals by locks, and some scheme would have to be devised for refreshing the lower lying water. The designs of the western garden towns after World War II exhibit a greater independence of the two elements of continuous building rows and traffic. These designs are also the first to include water in the public space. The original dike forms the main urban line in the design of Osdorp, with the traffic structure (which visually sets down lines to important buildings in the city centre) oriented perpendicularly. This rational treatment of the terrain as a basis for the town plan was facilitated by the hydraulic filling of the area. The raising to the traditional outlet water level as envisaged by Van Eesteren was cut back in 1950 because of the high costs involved. The western garden


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towns therefore have a polder water level and a far greater water surface area than foreseen in the original design. Both in Japan and the Netherlands water had to step back from the spatial arena after the war, not only by the filling in of water to give space to the exploding use of cars but moreover by the use of new technology that made surface water less necessary. The uncontrolled sprawl and the development on a lower scale in Japan, wherein the original polder structure with ditches was usually kept, offered better conditions than in the Netherlands. The lack of urban design, as a discipline that thought, designed and built not only an urban area but also a social area, in Japan was conditioned by a lack of public responsibility, civil culture, for this. Some New Towns, as a social and urban construction, were built but uncontrolled sprawl taking over the paddy fields was most common.

2.6 TOKYO REGENERATION OF A WATER CITY (1973–2007) 2.6.1 Late Sho-wa (1973–1989) and Heisei On January 7, 1989 the longest reign, Emperor Sho-wa ruled since 1926, of all Japanese emperors ended. The current era is Heisei era that started just one day after the death of Hirohito and his son, Akihito, succeeded to the throne. In accordance with Japanese customs, Hirohito was renamed ‘Emperor Sho-wa’ on January 31, as will Akihito be renamed ‘Emperor Heisei’ after his death. This paragraph goes into the important changes that marked the Late Sho-wa period and the culmination of one of the most rapid economic growth spurts in Japanese history after 1989. The bubble was built by keeping interest rates low, which drove Tokyo property values up by 60% within the year. By 1991 Japan’s famed ‘bubble economy’ burst and Japan experienced the ‘Great Slump in Heisei’. Recently Japan’s economy is emerging from the slump. 2.6.2 1968 City Planning Law The absence of planning and the cumulating urban problems described in the former paragraph were at the birth of the 1968 new City Planning Law. In basic form it continues the 1919 law and is directed at rampant urban sprawl. Two important new features are ‘senbiki’ and development control. The sprawl at the urban fringe should be accompanied by sufficient roads, sewers, parks and schools (Sorensen, 2002, 213). The City Planning Law 1968 introduced five major changes: 1. 2.

3. 4.

The delegation of planning responsibilities to the prefectures and municipalities. Introducing UPA (Urban Promotion Area) where urbanization was welcome, and UCA (Urbanization Control Area) where it was prohibited. They ‘drew the line’ (senbiki) between these areas. Development permission system and standards for public facilities. Allow public participation in planning.

Furthermore it consisted of a sophisticated zoning system with eight zones: 1. 2.

Exclusive residential (only ground bound, no mix), Exclusive residential (adding high rise to zone 1),

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Figure 2.29 Sprawl development in UCA Chiba shows a wide variety of loopholes allowed development to continue in relatively unrestricted manner Source: Sorensen, 2002

3. 4. 5. 6. 7. 8.

Residential (adding public facilities to zone 1 and 2), Neighbourhood commercial, Commercial ( all of the above), Light industrial ( all of the above), Industrial ( all of the above), Exclusive industrial (Sorensen, 2002, 221).


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The zones are based on exclusion not on separation of functions, which is a very different from western zonings that are based on the separation of functions. That meant that the mix of functions still occurred. With the 1968 law there was for the first time some prospect of effective planning through control over development but the central government’s dominance continued by legal controls, financial controls and personal transfers (Sorensen, 2002, 214). Even though duties and responsibilities were delegated to the local governments, overall strategy and policy as well as implementations was to reside with the central government (Sorensen, 2002, 216). Local governments actively promoted LR in less built up areas of UPA. Development permission was an important counterpart to senbiki, the tool was to make sure development in UPA was carried out in a planned and orderly manner. It was a novelty that planners had legal authority to hold measures to be met, like sewer and sufficient roads, or cancel the project (Sorensen, 2002, 217). Some developments still were uncontrollable because they fell under regulations like parking lots, scrap yards, building material facilities, and industrial waste facilities because they required no buildings (Sorensen, 2002, 218). Also the Development Permission encouraged small developments (under one ha) over the larger because those had to devote a larger part to public use (Sorensen, 2002, 219). Larger landowners have a high level of participation backed with almost a veto power. Moreover zoning covered only the type of land use, the Floor Area Ratio (FAR) and the coverage ratio (Sorensen, 2002, 220). The new planning law 1968 provided tools for planners and was mainly focussed on problems of rapidly growing suburban fringes (Sorensen, 2002, 223). In 1969 the Urban Redevelopment Law aimed at the improvement of already built up areas and the 1970 Standard building Law made detailed regulations backing the zoning system of the 1968 law. 2.6.3 Pollution diet There were three external factors in the early 1970s that ended the rapid economical growth and changed the political climate and the planning of environmental regulations abruptly. The first was the opening of diplomatic relations with China, the second was abandoning the dollar exchange rate peg (1971) and the third was the oil crisis after 1973. Japan’s lack of energy resources (in the form of oil and gas) makes it heavily dependent on import, which was painfully obvious in the 1970s. They started to focus on more efficient use of fuels and recycling (Sorensen, 2002, 226). The industrial growth and uncontrolled urbanization of the 1960s increased the environmental problems. The polluted water in Tokyo became unbearable for the public and a small political swing set in. In reaction to this shift the sitting government tried to reroute their policies into a more environmental path. Together with the 1968 law, the 1969 Urban Development law and the 1970 Building Standards law were part of extensive legislative initiatives for environmental management or the so called Pollution Diet (of the 1970s) (Sorensen, 2002, 224). These movements suggest that the government was finally more responsive to public pressure and electoral challenge (Sorensen, 2002, 210). The Pollution Diet was in total fourteen laws supported by the new Ministerial Agency of Environment, the National Land Agency (1974) and the National Land Use Planning Law.

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The National Land Agency took over several existing governmental planning functions and established long term land use programmes at national, prefecture and municipal level. They monitored land sales and urban land price inflation through land transaction controls (Sorensen, 2002, 243). One of the laws was the Water Pollution Control Law, based on ‘polluter-pay-principle’. A basin-based sewerage master plan scheme was introduced regarding pollutant reduction to attain the water quality standard in designated waters. These schemes gave industrial sectors very strong incentives to introduce ‘clean production’ with in-factory waste disposal/treatment system installation. The final return was rather higher contrary to their wishes, although many economists worried about the minus impact by such investment. It was realized that the new investment to in-factory waste disposal/treatment system boosted GNP to a higher level than expected with their eco-friendly products welcome shortly in the market. In addition, eco-industries have expanded their businesses to grow to a 10-billion Yen market in 1990s (Matsushita, 2007). In 1970 the Land Planning System (by the western world considered as imposing and greatly criticized) enforced (and authorized) by the National Land Use Planning Law provided five interlocking plans covering urban, agricultural, forest, park and nature conservation. These were developed under the National Land Use Guideline and the General Land Use Plan of the prefectures. The National Land Use Agency had to manage these plans directly supervised by the Prime Minister’s Office (Sorensen, 2002, 244). The original product of the NLA was the 1977 Comprehensive National Development Plan (CNDP) that was part of the movement of the early 1970s ‘building a new Japanese boom’. It was concentrated on the Pacific Belt Region and promoted train, highway and bridges. In 1977 an altered approach is recognizable from large scale transportation systems to the development of social and service infrastructure of local areas to keep the flow to metropolitan areas. The Ministry of Construction ‘aimed to enhance historical, traditional and cultural characteristics of regions, and focussed on improving living environments rather than on infrastructure of industrial project implementation’. Shimokobe Atsushi, a senior planner at the NLA, proposed development to be based on the drainage region to encourage social sustainability and quality of life, and balance between water resources and water demand for agriculture and industries. This settlement zone concept mixed the famous American new Deal Tennessee Valley Authority approach to regional development planning with a Fourierist Utopian vision of integrated and sustainable communities and proposed that Japan should be divided into 300 planning regions where nature and human settlement could be in balance. The idea even had a resonance with Japan’s feudal past when about 300 feudal domains had been very much based on the river basins and control over water supply had been the source both of sustainable rice agriculture and of political power (Sorensen, 2002, 249). Lack of money and power by the NLA spoiled this plan. It was displaced by the need to plan for World City Tokyo, a new CNDP came in 1983 (Sorensen, 2002, 250). At the end of the 1970s problems with the new planning system came forward; it failed to halt the worst problems of sprawl (Sorensen, 2002, 225).


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The four key factors that were compromising the planning system were: 1) Over designation of UPA. 2) Failure in proposing tax reforms. Farmers could divide their land into small pieces and sell them to developers who were not required to implement public facilities due to the fact that it was smaller than one ha. Most paddy fields had the size of a Tan, which is 991.7 m2. The farmers could hold on to their land as long as possible and sold small bits and pieces, showing the legendary political power of farmers in Japan. The profit was that the tax on farmland was less than tax on urban land. 3) Creation of loopholes that allowed sprawl in UPA and UCA for example the above mentioned mini kaihatsu, the development of a single paddy field. Because no public facilities were required these developments (one tan kaihatsu) had no sewer, gas, water, and one unpaved small (four meter) dead end road for enclosing 12 houses (60 m2), making a total of 896 m2. All these little developments were knit together as a string along rural lanes. 4) Very loose planning regulations in non senbiki areas (Sorensen, 2002, 232–237). The most important change in the 1970s was the shift of population from central city areas to the suburbs that was almost entirely structured by rail commuting (Sorensen, 2002, 251). In planning the major shifts were the building height limits and the protection for sunshine rights. The building height limit was 30 meters in urban and 10 meters in residential areas. There was no limit in commercial and industrial areas. The legal protection against sunshine rights was one of the first successful citizens protest and lead to the mobilization of urban development and governmental action. Since the 1970s there have been more organizations for local environment and quality of life which mark the upcoming civil society (Sorensen, 2002, 253). 2.6.4 1980s The period after the 1970s is framed by the elections in 1980 and the starting of the burst of the bubble in 1990. In this period all the trends concerning regulation increase on land development and environmental pollution and expanding social welfare and that were aimed at during the 1970s were reversed (Sorensen, 2002, 256). A clear result of the 1960s and 1970s movement towards a greater environmental consciousness, stronger pollution control and more effective city planning was the District Plan System of 1980. It was designed to solve a structural weakness in the 1968 law that caused a lot of problems in the 1970s. There was no detailed control over urban development or redevelopment like the layout of new roads (the only rule was the four metre width), there was no regulation for the size, the form, orientation and design of buildings (the only envelop was relatively generous) and no legal basis to prevent subdivision and redevelopment of urban plots (Sorensen, 2002, 264). The District Plan provided legally binding plans to control future road layout in undeveloped areas. In existing built up areas it was more difficult because there was no legal way of opposing any development that conformed to zoning and building standard laws. This resulted in the boom of high rise condominium development (mansion boom) (Sorensen, 2002, 265). The District Plan was based on the German Bebauungs-Plan and made new restrictions possible like a new road layout, lot sizes, building design, building setbacks and construction materials.

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Figure 2.30 The mansion-boom also produced great scale differences co-existing in for example Fisherman Warf in Tokyo with the traditional housed on the right surrounded by super high rise Source: Fransje Hooimeijer

It contained two parts, the statement of policy intends, and the district improvement plan that regulated private development and public facilities. It was the first time local government had legal power to impose more detailed restrictions on private developers that allowed a zoning and building standard system such as: use, maximum and minimum lot coverage, building height, FAR, setbacks from property lines, shape and design, material colours and styles and landscaping (Sorensen, 2002, 266). The new powers enabled some local governments to develop methods of community based planning and public participation during the early 1980s. These are often referred to as Machizukuri, community building/development (Sorensen, 2002, 268). An example is the Setagaya Machizukuri Ordinance (1982) an influential simple model. The major can designate the Machizukuri Promotional Area in consultation with the local residents. A Machizukuri council is then formed to represent the local residents that will review the assembly of the District Plan (Sorensen, 2002, 269). From the 1980–1985 dominant growth of Tokyo new service sector had a profound influence on Japanese urbanization and planning (Sorensen, 2002, 260). The fourth Comprehensive National Development Plan (1987) was fixed on renewed concentration of jobs and people in the Tokyo region and its corollary of population decline and job shortages in local regions and applied from 1986–2000 (Sorensen, 2002, 261).


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The concept of Technopolis and New Town like Tskuba (follow up from the sleep towns of the 1960s) was the first attempt to combine economics with planning and social quality. The government ministries finally acknowledged that high quality residential environments were worth investing in. In 1988 according to the trend of government budget cutting and deregulation the law was amended to allow more flexibility in FAR and lot coverage. On the one hand it also improved the District Plan because it broadened possibilities for example the ‘Special District Plan for redevelopment’ of old industrial sites or for example in dealing with project developers trading more FAR for more land for road widening (Sorensen, 2002, 267). The 1980s are representative of deregulation and administrative reform with conservative and pro business ideology. The external trade surpluses are pressured internationally to secure them. The domestic, political and economical pressure rises to expand spending on pork barrel public works projects. Deregulation, opposed by local governments and citizens, was achieved by loosening the zoning regulations, for example shrinking cities could abandon the senbiki system (Sorensen, 2002, 272). 2.6.5 Liveable water fronts The regeneration of the water in the city started in 1970 when better quality made it possible to keep events at the Bay of Tokyo. Regattas and fireworks brought a lot of people to the waterside. Also nature along the water became part of the regeneration in the early 1980s when Odaiba Sea Park was opened. The river and bay as an ecosystem provided the citizens with outdoor space for sports and picnics became a valued aspect. When factories moved out the Bay area in the early 1980s the voids were filled in by housing. Outside the city centre these waterside locations were discovered for their favourable living conditions. The regeneration of Tokyo as a water city was then marked with the pedestrian bridged Sakurabashi along the Sumida River in 1985 (Jinnai, 2004, 50). Another example is the River City 21 on the location of the Ishikawajima Shipyard of Ishikawajima-Harima Heavy Industries & Co. at the estuary of the Sumida River. This transformation was based on the Okawabata strategy meaning that the owner, the Mitsui Fudosan Group, considers housing leasing operations as an important business along with housing sales operations, and focuses its efforts on the extension of the scope of business by developing and managing investor-oriented high quality rental housings. This securitization and private fund scheme is an innovative measure to introduce institutional investors’ capital into the rental housing market, which is expected to become a key factor to promote liquidation and activation of the real estate market, as well as to contribute to the further expansion of our housing leasing operations. At the same time containers came into use for the transport of goods and the warehouses were being abandoned. In the same fashion as Soho in New York these empty warehouses attracted artists to live in their ateliers and lofts. Waterfronts like Okawabata, Fukagawa, Tsukishima, Shibaura and Shinegawa were transformed by these cultural communities into lively urban places with lots of restaurants, galleries, cultural activities and an extensive loft culture. Both developments, new housing on emptied out factory sites and the loft culture were accentuating a true ‘waterfront boom’ (Jinnai, 2004, 61). Late in the 1980s the information society advanced Tokyo as a representative financial centre and the demand for office buildings exploded. Also here the Bay area was

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Figure 2.31 In the background the waterfront development from 1980. In the foreground they are preparing the building site of the new island.The picture is taken from the subway making an excellent connection around the new islands. Source: Fransje Hooimeijer

found fitting for the construction of tall office buildings. It transformed the low dense warehouse area into a high dense office district. Examples are many: MM21 in Yokohama, Makuhari Messe in Chiba and Tokyo’s Waterfront Sub Center Plan (1985–1986) on the site of Tokyo Teleport Town. After the bubble burst in 1990 the waterfront development became less interesting for offices and projects in the city, such as Roppongi Hills, Marunouchi Building and Shiodome, were developed (Jinnai, 2004, 62). It was not only concentrated on the waterside but also on the water. There were projects to a sub-centre on the water, for example Tokyo Teleport Town or Odaiba project the seventh sub-centre on the island. Odaiba was originally constructed in 1853 by the Tokugawa shogunate as a series of 6 fortresses in order to protect Tokyo from attack by sea. In 1928, the Dai-San Daiba or ‘No. 3 Battery’ was refurbished and opened to the public as the Metropolitan Daiba Park, which remains open to this day. The modern redevelopment of Odaiba started after the success of Expo ‘85 in Tsukuba (the Technopolis). The Japanese economy was riding high, and Odaiba was to be a showcase of futuristic living, built at a cost of over $10 billion. T3, as it was nicknamed, was supposed to be a self-sufficient city of over 100,000 residents. When the bubble burst in 1990 Odaiba was rendered virtual wasteland, under populated and full of vacant lots. In 1996, the area was rezoned from pure business to also allow commercial and entertainment districts, and the area started coming back to life as Tokyo discovered the seaside it never had. Hotels and shopping malls opened up, several large companies including Fuji TV moved their headquarters to the island, and transportation links improved.


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Figure 2.32 Tokyo’s Waterfront Sub Center Plan (1985–1986) on the site of Tokyo Teleport Town Source: Fransje Hooimeijer

2.6.6 Hachioji Minamino City Hachioji Minamino City (in Hachioji-shi in Tokyo is situated in the hills of the Tama district south from city centre of Hachioji, and about 40 km west of Metropolitan Tokyo. The area of development is 394.3 ha and the expected population and number of houses respectively 28,000 persons and 8,450 houses. The site is 110 to 210 metres above sea level and there is 100 meters in difference between highest and lowest points. In 1988 the ground works started with earth cutting a soil volume about 1,1000,000 m3, the soil volume for earth filling was about 1,1700,000 m3. To prepare the site Kanto loam (64%), Sand (17%) and Clay (7%) were used. It is designed with the concept of ‘five mountains, five hills, three mountain streams and one river’. This stands for the town making use of the natural environment that is unique to the district. The Hyoei River flowing through the area is managed using a water circulation recycling system, and the run off of storm water during rain is controlled. On the banks and riverbeds several efforts are made to enable aquatic organism to settle. Not only in a physical but also in a social sense the aim is to use the natural environment by teaching the inhabitants about know-how and technology related to the surroundings. This interchange helps to cultivate the living environment and the symbioses of infrastructure and people. This approach has a far reaching reputation and has been awarded with the Prime Minister’s Green Urban Award in 2002 (Urban Renaissance Agency, no date). 2.6.7 Otsu lakeside Nagisa Park Otsu lakeside Nagisa Park is located on the west side of lake Biwa in Otsu-shi, Shiga Prefecture. Between 1987 and 1999 it was reconstructed based on the concept of ‘Waterfront Town Development’, outlining Otsu City’s ideal image of a city. In construction and maintenance of the park great effort has been taken to minimize the impact on

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Figure 2.33 Tokyo’s Waterfront Sub Center Plan (1985–1986) on the site of Tokyo Teleport Town Source: Fransje Hooimeijer

the environment. The added sand and earth for land formation over the lake has been separated from the original lake banks with a muddy colour prevention coating and waterproof mat. The features of the lake such as the water purifying function and the native habitat of living organisms have been successfully constructed. The design of the public space along the water is another important feature. The total of 4,8 km of waterside is attractive and functionally designed. The park was awarded the annual scenery award ‘Minister of Construction Prize’ in 1995 (Urban Renaissance Agency, no date). 2.6.8 Naha Shin Toshin The subtropical setting and symbiosis with the environment makes Naha Shin Toshin (1989) in Naha-shi, Okinawa Prefecture a good example of a Land Readjustment project. The aim of the project is to establish a new city centre and the development of a former U.S. army residential district. For the water source, groundwater is stored by installing pavement that allows rain to penetrate into the ground easily. State-of-theart technology is used to supply recycled water to public facilities, and commercial and business facilities which measure above 3000 m2 of total floor space. A stormwater reservoir tank is installed under the parking area of the park, run by Naha City to supply water for restrooms and the sprinkler system. In public facilities, the water is used for the eco ice system used for night power and photovoltaic generation systems, as well as for greening rooftops and walls (Urban Renaissance Agency, no date). 2.6.9 Hokusetsu Sanda Woody Town The creation of a high quality waterfront space in 1973 has been very successful in Hokusetsu Sanda Woody Town in Sanda-shi, Hyogo prefecture. The core of Kobe


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Figure 2.34 Hachioji Minamino City Source: Urban Renaissance Agency

Sanda International Park City includes various parks full of nature, which takes advantage of an ancient burial mound, large pond, and forest in the area. Along the banks of the river Hiratani that crosses the park are seven squares with an easy access to the river water. The waterfront is used to relax and enjoy the natural environment.

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Figure 2.35 Otsu lakeside Nagisa Park Source: Urban Renaissance Agency

A storm-water reservoir system is installed in the parks underground to ensure that water is fed continuously to the river, even during the dry season, and stormwater does not flow excessively into the river during heavy rain (Urban Renaissance Agency, no date).


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Figure 2.36 Naha Shin Toshin Source: Urban Renaissance Agency

2.6.10 Burst of the bubble The bubble economy was an economical balance that was enforced by factors like the regulation of land prices, making them higher and in giving out of mortgage loans based on that value. The privatization of government owned corporations and the sale

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Figure 2.37 Hokusetsu Sanda Woody Town Source: Urban Renaissance Agency

of government land made the land prices inflate (Sorensen, 2002, 280). There was not a real burst but rather a slowly deflating of the bubble. Stock prices crashed in 1990 followed in 1992 by a drop in land prices and slow devaluation ever since during the ‘lost decade’ (1990–2000) until 2001 (Sorensen, 2002, 286). Land price inflation became more serious and more widespread rather than deregulation, stronger land


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law and land controls were necessary to control land speculation and stop the rise of land prices (Sorensen, 2002, 287). The bursting of the bubble brought great discredit to the central government and led to the call for decentralization of the planning authority and the change of the planning law in 1999. Also pressure increased for a better quality of life in urban areas and more effective urban planning measures. The growth in voluntary activity, non governmental, non profit organizations, and citizens’ movements directed at environmental improvement also established a civil society in the 1990s. Three important new planning practices representing a major shift in the urban planning came up: master planning, machizukuri and historical preservation. Municipal governments based involvement and a significant public participation in combination with a broader conception of public good and legitimated by public interest made this shift possible (Sorensen, 2002, 288). According to Sorensen (2002), during the 1990s the government spent useless or harmful budgets on ‘easy’ projects like bridges, tunnels and also coastal defences against erosion. Vast stretches of the Japanese coastline have been covered in concrete tetrapots (four pointed concrete blocks). Even though the Japanese coastline is frequently hit by typhoons and tsunamis (Japanese word for harbour wave) lining the coastline has been criticized as redundant, ecologically destructive and simply ugly. The reason is there is little opposition to coastal improvement and budgets can be spent promptly resulting in a much higher completion rate than other types of projects, adding the creation of jobs (Sorensen, 2002, 291). The changing political context of the 1990s made the pressure grow for decentralization and more local budget and power. Also greater freedom of non profit organizations and pressures from citizens’ organizations for better city planning authority at the local level was part of this context (Sorensen, 2002, 297). The 1992 amendment to the City Planning Act for new zoning categories that met local conditions was denied, instead four new zones were added. Amendments in 1999 and 2000 were respectively arranging the abolition the delegated functions of local governments, they were no longer an ‘agent’ of the central government and the introduction of the ‘suggestion system’ in which citizens could make planning suggestions (Sorensen, 2002, 298). 2.6.11 Municipal Master Plan The Municipal Master Plan was a product of the bubble economy and the first time plans included a map! (Sorensen, 2002, 300). Most municipalities had little experience with urban planning, so this Master Plan was quite radical for Japanese city planning. The long term vision, the financial policies and the requirement for public input took time to get accustomed to. Rather a contrast with the top down rigid communist/capitalist tradition of the Japanese way to deal with spatial structures with only interest in public facilities (roads) and zoning. The second problem for municipalities was the lack of budget and the third was the question of what public participation should be allowed (Sorensen, 2002, 303). Some experience with local planning was with the ‘development manuals’, machizukuri, that were written by municipalities (about roads, schools, sewers etc.) since the 1968 law. They were more specific, and with higher standards than the City Planning Law

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and the Building Standards Law. They were not legally enforceable but based on a system of ‘advice’ and ‘persuasion’. These are variations on the famous Japanese practice of ‘administrative guidance’ or extra-legal bureaucratic arm-twisting and back scratching. Project developers usually found it easier to cooperate than to fight against the will of the local government. Also the manuals were supported by local citizens so moral high ground against developers could be found (Sorensen, 2002, 310). Thus, besides the formal national laws, the municipalities used informal local ordnances and machizukuri and from the 1980s the District Plan, Land Use Control and historical protection rules. The informal laws became legal in 1999/2000 (Sorensen, 2002, 312). Even though different instruments are developed, the fundamental problem of Japanese city planning remains the power of landowners (Sorensen, 2002, 332). 2.6.12 Recovery of the relationship between nature and city In 1653 the Tamagawa Canal was dug, taking water from Hamura, into in the upper reaches of Tama River and was flowing into Edo castle. It was 48 km long and meant for irrigation of the paddy fields, water supply, and established a city framework within its numerous diversions that is still retained in Tokyo today (Kamiya, 2004, 64). Tokyo Metropolitan Government held an exhibition Tama Life 21, showing a city concept based on water and green networks and formulating the collaboration between citizens, government and researchers. The project offered a basis for community planning through the cooperation of these parties. The project aimed to foster shallow groundwater by regenerating river water in Tama River where water after sewage treatment flows and diverted to channels that were almost running dry, as well as renovate spring water and rivers. The green aspect was filled in by accompanying these waters by a useful park for the inhabitants (Kamiya, 2004, 65). City development today is focusing on roads, reflecting a motorized society. In contrast with rivers and canals, roads can never create an ecosystem. Pursuing the water cycle is naturally opening up a vision of a whole city, reconsidering the relation between human ecosystems and natural ecosystems: water system planning (Kamiya, 2004, 67). In 1997 a discussion between six ministries and nine institutions resulted in the conclusion that there should be a water ministry and water laws. The way of looking at the water is different in civil engineering and in architecture. For Tokyo eco regional design is considered to present linkage among ecological industries of the whole metropolitan area as well as the city centre, and vision of informational society without the gap between city and region, by gaining a foothold in environment for economic revival (Kamiya, 2004, 68). Already far back into the history we can find the eco regional design for Edo of Ieyasu Tokugawa in early modern age as the base of city planning. He first investigated the potential of the water and eco system, after that he planned the city along those measures. Again Tama River one of the key aspects in the prosperity of Edo, can be that for Tokyo today (Kamiya, 2004, 68). Recently, flooding avoidance has been taken into consideration at the stage of the regional planning in Japan. Hazard maps with potential risks educate the residents and are suitable for regional planning of local governments in vulnerable regions. These measures can reduce the disaster damage in calamity and economical sense and can provide methods for evacuation. It is better to change the concept of residence and live with disasters at the same time (Haruyama, 2005, 12).


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Table 2.1 Evolution of Japanese land use zoning categories

Source: Sorensen, 2002

Water quality standard and pollutant emission standard is under responsibility of Ministry of Environment plus flood-control and sewerage projects have been implemented by Ministry of Land, Infra-structure and Transportation. The River Law is revised in 1997 in order to comply with such a recent request as conversion to natural eco-system-preserving-type river improvement and dam construction, restoration of natural water cycle, etc. In order to materialize these tasks, a ‘public-private-partnership’ is introduced. Hereinafter, many associations are organized

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Figure 2.38 Sun Varie Sakurazutsumi (in Musashino-shi,Tokyo) Source: Urban Renaissance Agency

to boost public involvement in planning and designing of river management systems. In the municipal level, the leading local governments prepare for more comprehensive basin management systems. The most advanced is the 50 year master plan named ‘Mother Lake 21’ proposed in 2000 by Shiga Prefecture, where first World Lake


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Conference was held in 1990. As suggested in this master plan, it is necessary to make a continuous operation of total systems, either structural or non-structural. In addition, it becomes more feasible, if there could be a strong consensus among local sectors that local aquatic environment should be their ‘common value’ to be preserved from the long-term vision (Matsushita, 2007). 2.6.13 Urban and water designs Urban design as a public tool to control urban quality arose with the rise of civil culture. Not only municipalities but also public institutions start to pay great attention to this. The Incorporated Administrative Agency Urban Renaissance Agency (URA) is erected in 2004 coming from or the continuation of several other corporations. The Japan Housing Corporation was established in 1955 under the aim of creating a sound urban area by implementing large-scale land development projects for workers faced with difficulties in finding housing. For this reason a number of collective housing complexes were constructed, mainly in large cities. In 1981 it became the Housing and Urban Development Corporation that continued this activity and added the development of urban areas, redevelopment of cities and the development of parks. Also taken into the Housing and Urban Development Corporation was the Land Development Corporation that started in 1975. This public service was aiming at stabilizing the daily lives of residents and promoting welfare through large scale creation of housing land and public facilities as well as development of means of transportation in areas surrounding large cities. The Housing and Urban Development Corporation became the Urban Development Corporation in 1999 and was one of the base corporations that started URA in 2004. Also part of UR became the Japan Regional Development Corporation (erected in 1974) that was meant for realizing a well balanced development of domestic land and promotion of the region by providing assistance to disperse populations and industries highly concentrated in large cities to regional areas and facilitating self-sustaining growth of regional industries. The Urban Renaissance Agency is engaged in efforts for the realization of urban redevelopment as an Urban Renaissance Producer based on the techniques and know-how cultivated by the Urban Development Corporation (Urban Renaissance Agency, 2005, 22). It aims at an ‘urban renaissance’ into producing beautiful, safe and comfortable cities, providing coordination and partnership to businesses in the private sector. They have 770.000 rental houses that they took over from the Urban Development Corporation. Sun Varie Sakurazutsumi (in Musashino-shi, Tokyo) is a project of the URA wherein the reproduction of waterfront space must upgrade housing complex (of 601 houses) built almost 40 years ago. Even though the complex was surrounded by rich environmental assets like cherry blossom trees and other trees, the Sengawa River which cuts right through the premises (44.000 m 2) was a concrete canal without any water. By transforming it in 1999 into a natural river with banks in gentle slopes and natural stepping stones it was reborn as a environment for various organisms, and an aqueous space at which people could gather (Urban Renaissance Agency, no date). Saitama Shintoshin (Saitama-shi Saitama Perfecture) is located at the centre of the Kanto Plain, serving as the major intersection for a wealth of activity stretching from the capital to a wide area covering the central and northern regions of Japan. The transfer of several national government institutions coupled with the concentration of

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advanced business, commercial and cultural functions will enable this new urban centre to lead the way in the reorganization of the Greater Tokyo Metropolitan. The project started with the closure of the former Japanese National Railways Omiya rail yard in 1984. Two years later they designated the core business cities in accordance with Tokyo Metropolitan Basic Plan and again two years later the transfer of certain government organizations to the site of the old Omiya railyard was final. The same year land readjustment project districts were established with expressways and access roads. The approval of the LR, the land was now owned by the Saitama Prefecture, was in 1991 and the groundbreaking ceremony for the Saitama-Shintoshin project was held. The draft of the basic adjustment plan for Saitama-Shintoshin central facilities and core facilities was done in 1994, the project is now 10 years under way, and a winner selected in competition for Saitama Hiroba (provisional name) and Saitama Arena (provisional name). Construction started in 1996 with first the Saitama-Shintoshin National Government Building, Saitama-Shintoshin M.P.T. Building, Saitama Super Arena and in 1997 Saitama-Shintoshin declared a barrier-free city. After that one after the other the buildings popped up until today. In 2000 the commemorative ceremony celebrating and the opening of Saitama-Shintoshin accompanied the arrival of the first users. An important aspect of the general planning of Saitama Shintoshin is the aim to be a people and environmentally friendly city. Efforts are made to develop a resource recycling system of the whole city with the collaboration of construction companies. As a water resource, groundwater is cultivated through road pavement methods, which let storm-water infiltrate: storm-water accumulated temporarily in balancing reservoirs to reduce flow-out is used to build streams for wetting urban space, and vaporization of water is promoted by the greening of the population infrastructure. In the future, intermediate water supplies recycling sewage water will be installed (Urban Renaissance Agency, no date). Another factor after the ecological shift in the 1970s was that water started to be seen as part of the public greenery, which is scarce in Japan. For instance, the Kitazawa River has been brought back above ground at the request of the residents of a Tokyo neighbourhood near Ikenoue train station. The Kitazawa River flowed underground through two large conduits and its main function was as a sewer. The district residents wanted the water to be visible again in the neighbourhood. The municipal government therefore created an elegant stream on top of the conduit, in consultation with the residents. The stream is fed from the outflow of a purification plant 17 kilometres away. An important aspect is that each local neighbourhood of 100 to 200 residents has produced its own design for their part of the stream, which has created extraordinary diversity. This is a good example of tenant participation, and the successful demonstration is prompting many more neighbourhoods in Tokyo to copy this facility. Another example of water and urban integrated design is the super levee that is more closely studied in chapter five. The Ministry of Land, Infrastructure and Transport (MLIT) is transforming sections of dikes – some of which are only 200 to 300 metres long! – into super levees. They are working closely with the Tokyo Metropolitan Government Spatial Planning Department. The Tokyo Metropolitan Government is negotiating with the landowners and homeowners behind the dike and is either buying them out or arranging temporary accommodation so that they can return after the superlevee construction. Rather than an uncoordinated building there will be a park and a high rise building.


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Figure 2.39 New urban block in Saga Source: Fransje Hooimeijer

Figure 2.40 Traditional roofs in Kanazawa Source: Fransje Hooimeijer

2.6.14 Water is still an evident element of urban space Even though urban design is becoming a part of Japan’s daily urban practice the plotwise way of expanding cities continues, like for example in Saga. The same goes for water as an element of public space, somehow it is in the blood of the Japanese to have water integrated in all types of artefacts. To start with the roofs of Japanese houses, build up from different smaller roofs making a water ballet. When it rains the water

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Figure 2.41 Traditional rain water discharge gutter in Kyoto Source: Fransje Hooimeijer

Figure 2.42 Rain water discharge integrated in the pavement (around the Tokyo Dome), being kept clean extremely well Source: Fransje Hooimeijer


Figure 2.43 Small canal in Kanazawa Source: Fransje Hooimeijer

Figure 2.44 Canal as part of public space in Kanazawa Source: Fransje Hooimeijer

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Figure 2.45 Water square in the park near the castle in Tokyo Source: Fransje Hooimeijer

will fall down on the different parts of the roof and will make the water not only more visible but also the sound is louder. Also, or maybe especially, the pavement in Japanese cities often holds separate visible lanes for water, an open gutter. Already in the traditional cities these gutters were made of stone, like the Romans, with stepping stones for the entrance of the houses. The water can be made visible due to the self-reliance of urban neighbourhoods they are always kept clean. Many other artefacts can be found all around the county, in Kanazawa you are even welcomed by a fountain saying welcome and also telling you the time. 2.6.15 Comparison with Dutch water cities The refinement of technology in the last decades of the twentieth century has made it possible not only to maintain that which is threatened, but also to elect for an increasingly vulnerable place in the game between water and land. The awareness that this high technology makes us lose sight of what is vulnerable marks a cultural change at the end of the 1970s towards greater attention to the environment and ecology. In the Netherlands the notion of integral water management is brought up and it is assumed that ground and surface water must be managed in a physical sense as well-founded systems (physically, chemically, and biologically). Integral water management means a shift in regime for civil engineering. It leads to new objectives requiring new designs and working methods. It also means a strategic regrouping, as together with civil engineers, biologists, and ecologists have also become players in the field (Schot, 1998, 63 and 181–192). In many countries there are similar institutes and consulting companies that specialize in soil mechanics. Usually they also deal with foundation engineering, which is concerned with the application of soil mechanics principle to the design and the construction of foundations in engineering practice. Soil mechanics and foundation engineering together are often denoted as Geotechnics.


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Many different piles and techniques to drive them in have been developed, and new techniques building site preparation have come into use. The use of lightweight materials such as polystyrene foam and granules has the advantage that building can start immediately and that little subsidence occurs afterwards. Webber and Rittel mark the change, the end of the idea of efficiency, at the end of the 1970s when the urban context was reintroduced. In response to the technocratic approach to urban design in the 1950s, it was in the 1970s that the ecology of water returned to the attention of the urban designer (Webber and Rittel, 973, 158). The issue of ‘urban identity’ appeared on the political agenda, and led to the conclusion that water was an important component of the identity of the old Dutch towns. Since the 1970s, numerous plans have been developed and executed to restore earlier watercourses. For example, part of the old encircling canal in Utrecht was dug out again after having been filled in for traffic. Unlike the austere canals of the post-war reconstruction, the natural character of a strip of greenery with water blended perfectly with the 1970s ‘woonerven’ (home zones). Houses were arranged around courtyards and surrounded by green structures with singels. The natural character of water was used enthusiastically in the design of the water structure and the profile. The wildlife-friendly banks that became popular in this period altered the appearance of the singels considerably. One of the reasons for the return of nature in the city was the new profession of landscape architects that entered the arena of urban design. Landscapes structured were introduced as a base for the design, and water played of course an important part in that. In the past two decades, water initially received little attention but later made a comeback in the city. Public spaces became bleaker in the 1980s because of the economic slump, which had a great influence on the application of the waterway as a natural element. The positioning of the public space in the urban design was purely functional, and the profile of the canal was designed for low maintenance. No financial resources were available for high-quality public space, and the design assumes minimum maintenance costs. From the 1990s the effects of climate change and again the attention for history pushed the return of water in the city. Awareness arose that the Netherlands is a water machine that needs to be approached spatially, not only technically. Urban designers took great interest in working with the water task as the basis of their urban design. On the other side civil engineers needed to let go of their strict control and start to adapt to the natural rules of the water. The most recent law, the Watertoets (2003) [Water Test], compels new expansion districts to comply with certain hydraulic conditions, which were reviewed by the Water Board. This is also how the regional scale of water control is organized, as here the law of communicating vessels applies: if one fiddles with part of the system, this will influence the complete system. For this reason many municipalities have created a Water Plan, which also maps the hydraulics in the existing city, sets guidelines, and defines future spatial issues. With regard to polder cities the emphasis is on maintenance and storage instead of the transferring of rainwater like it is common in Japan. For example there, temporary water reservoirs in public areas are used for polder cities, in the form of green roofs which can temporarily retain water (such as grass roofs), reservoirs to collect rainwater for use as toilet water, more gardens and ponds instead of tiled terraces, and fully

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Figure 2.46 Water as backyard in IJburg Source: Tim Eshuis

built inner areas and more surface water in the district. The sewage and rainwater are to be collected in a ‘separate system’ or in buildings. Rainwater does not have the same level of contamination as sewage water and therefore does not require the same purification. Moreover, the sewage system cannot process the rainwater of a heavy storm. Particularly in old cities, such as Rotterdam, where a combined system exists, there are many problems with heavy rainfall. Such systems are slowly being replaced by separate systems. In many new development districts, surface water is given a structural role, as in the old days. In IJburg, the water serves as a backyard, positioned as a division between private and public areas. This natural boundary makes living next to the water as a natural fencing immensely popular, as it is often referred to as ‘real estate water’, since the water brings in money. Probably because of the more severe problems (due to climate and the fact that the urban pressure was much higher in Japan) the inventive urban rules for water management, like the Tokyo Dome, were grounded in Japan much earlier. When also urban design as a public tool to control urban quality arose with the rise of the civil culture, urban water projects were started. The Japanese projects described above are perfect combinations of innovative water management and urban design the current Dutch urban practice could take example of.

2.7 CONCLUSION 2.7.1 The Japanese Model Overseeing the history of planning in Japan it is possible to describe the planning practice in what Sorensen calls: the Japanese model. Characteristic for Japan is the consistent focus on state resources and economic development, a weak relationship of


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planning and civil society, dominance of central government, consistent preference for public building projects over regulations of private development activity and a long tradition of self-reliance of urban neighbourhoods (Sorensen, 2002, 333). The consensus is formed by an authoritarian basis of social control and Japanese group-ism is merely an expression of an effective system of social control (Sorensen, 2002, 335). The concept of planning as a tool to protect public welfare has never been strongly established in Japan. Instead it was a tool that extended state interest, resistance on interference with landowners’ rights is in this context logical (Sorensen, 2002, 338). Taking care of the living conditions has always been the task of the people and not of the government. The 1990s meant the rebirth of Japanese civil society and birth of machizukuri movements in support of local environmental improvement (Sorensen, 2002, 339). It is amazing that the civil society didn’t develop sooner out of this strong neighbourhood organization. The reason can be found in the tradition of the top down organization and not bottom up like in the Netherlands (Sorensen, 2002, 345). The people were used to the feudal order, to be obedient, no self assertion. Planning was not very effective because of the central power and the weak political support (Sorensen, 2002, 149). Neighbourhood organizations responded to the real needs of Japanese urban residents and are self organized. They have contributed enormously to the liveability of Japanese cities and are directly related to several very positive aspects of urban life: high level of personal safety, cleanliness, general friendliness, civility, all products of a strong community responsibility (Sorensen, 2002, 343). Quality of urban life became an issue with the environmental problems; the disaster forced a change and promoted civil society by activating protest (Sorensen, 2002, 203). For 1868–1900 there was bureaucratic absolutism, 1900–1936 limited pluralism, from 1936–1945 total civilian and military bureaucratic control. The skewed electoral system, weak local government, and the growth of central government power characterize the interwar period (Sorensen, 2002, 100). Strengthening social coherence for national force was done by the Local Improvement Movement. They tried to revive the responsibility system of the Tokugawa Japan, in which the local community had the shared responsibility for the payment of taxes, maintenance of public order and prevention of fires, and the maintenance of local public infrastructure like roads and wells. These local neighbourhood associations, cho-naikai (dominated by the old middle class), also organized local garbage collection points, recycling campaigns, sanitation and insecticide campaigns, street cleaning, installation and maintenance of streetlights, and organizing night watches against fire and crime. This vertical hierarchical connection from the top to every household was seen as a totalitarian control that was abandoned by the post-war occupation. They regrouped under a different name but with many of the same members and tasks but without connection to the government. These close-knit neighbourhoods were part of the success of Japanese cities against the Western urban crisis of the 1960s and 1970s of spiralling crime and abandonment of inner cities by the affluent. The cho-naikai are also the answer to the absence of an active middle class in municipal politics, because they were working at the local level (Sorensen, 2002, 104). The development of an international city planning was largely generated from the institutions of the civil society. In Japan planning was conducted by a small elite group within

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the Ministry of the Interior. Moreover stronger planning regulations were often vigorously opposed by landowners. Never like in European countries did the evolution towards a principle that public regulations of urban development were important to protect the public interest (Sorensen, 2002, 107). The Dutch model – when taking the Japanese characteristics – could be described as the consistent focus on economic development, defence (against water and foreign enemies) and rationalization, a strong relationship of planning and civil society, dominance of central government based on a strong civic society, preference for regulations of private development activity over public building projects (this has changed the past ten years) and no tradition of self-reliance of urban neighbourhoods. The Dutch group-ism is found in the fight against the water, illustrated by the erection of the water boards already in the twelfth century. In contrast to the Japanese group-ism this resulted in a concept of planning as a tool to protect public welfare. 2.7.2 Learning from Japan 2.7.2.1 Landscape as leading principle The way the Japanese and the Dutch dealt with the topography of their territory: used it to make it productive or usable for settlement, is highly comparable. Even the way the taxes were calculated based on the width of a lot connected to a public facility (street or waterway) are the similar. In both countries reclaiming land from water

Figure 2.47 Streets are kept clean and plants make them more liveable Source: Fransje Hooimeijer


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started very early and in both cases these areas were occupied by the lower class and industries. Also the redesign of these industrial (often harbour) areas in the past decades for urban use is seen in both countries and globally. The new cultural appreciation of these areas by the urban dwellers (meaning and character) and the physical quality of water make these popular water cities. 2.7.2.2 Control and urban design Like in Japan the Dutch cities define and locate themselves in relation to their broad natural setting and topography: water management. Dutch and Japanese cities differ from European cities in not exhibiting a centripetal structure by erecting tall structures with symbolic significance, such as towers and domes, in the centre of the city. Dutch and Japanese cities are built on the principles of their own group-ism that coincidently embrace the same type of rationalism. Probably control is the reason for this rationalism. The Dutch needed control over the water and in Japan the authoritarian basis of social control by the shogun. In the Netherlands this control was brought over towards a planning that considered public welfare and resulted in a strong tradition of urban design. In Japan urban design had remained absent until a decade ago, but the control did produce a long tradition of self-reliance of urban neighbourhoods with a high social quality. 2.7.2.3 Parallel switch The impact the railway and the car have had on the urban structures has been great both in Japan and the Netherlands. The transformation of water to land cities started in both countries in the period and has been transforming the cities throughout the whole twentieth century. Not only by starting to fill in the waterways but also by organizing urban growth and urban structure along the lines of the new mobility and not like the phases before using the rules of the topography of the territory. Both in Japan and the Netherlands water had to step back from the spatial arena after the war, during the Mid Sho-wa period. Not only by filling in of water to give space to the exploding use of cars but also by the use of new technology that made surface water less necessary. The uncontrolled sprawl and the development on a lowers scale in Japan, wherein the original polder structure with ditches was usually kept, offered better conditions than in the Netherlands. The switch to a more ecological approach of the city also paralleled in the 1970s after the oil crisis. The Japanese, still suffering from the Minamate disease reacted promptly with rules for buildings and new urban projects. 2.7.2.4 Cultural contradiction The strong private ownership in Japan on a lower scale and the public task of water management seem not to have any connection or conflict. In contradiction to the Netherlands where the public task of water has produced a strong common sense, polder culture, and governmental structures. In Japan the shogun dominated the social structure while in the Netherlands a great sense of equality, because one needed one another in the fight against water, still makes for a very liberal society.

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2.7.2.5 Urban design takes over The lack of urban design, as a discipline that designs and builds not only an urban area but also a social area, in Japan was conditioned by a lack of public responsibility, civil culture, for this. Some New Towns, as a social and urban construction, were built but uncontrolled sprawl taking over the paddy fields was most common. Today in Japan the move towards reconsideration of the city in terms of rivers is taking place, meaning considering it from an ecological point of view and restoring rivers. Not only in planning but also from the River Planning perspective direction changed to environmental and sustainable projects developed with a public-private partnership construction like the super levee. The Ministry of Construction made an amendment to the River Act in 1995 towards an approach that for the first time incorporated terms like ‘environment’ and ‘inhabitants’. The introduction of the ‘Naturnaher Wasserbau’ from Switzerland lead to the nature renovation project Tama River Improvement Plan and the project for Stream Investigation (Kamiya, 2004, 66). When also urban design as a public tool to control urban quality arose with the rise of the civil culture, urban water projects were started. The Japanese projects described above are perfect combinations of innovative water management and urban design the current Dutch urban practice could take note of. 2.7.2.6 Japanese boldness It is interesting to see how Japan is dealing with comparable water problems. Japan is demonstrating what is possible if you simply make a start and are willing to try out newly available techniques on a small scale, to improve them, and to apply them on a larger scale. They also have considerable faith in their ability to solve complex problems with large future uncertainties. They have a tradition of ‘doing’ whilst the Dutch first talk it over and provided everybody is in favour of the enterprise they start doing. A point particular worthy of adoption by the Dutch is the boldness to start a project without knowing for certain whether all of it will ultimately prove feasible. Boldness of this kind is what the Dutch ancestors possessed when they created their country from the water, but what is lost somewhere along the way. Constructing a super levee 200 metres long without knowing whether the other 27 kilometres will be realized is a clear example of this boldness. What would be said immediately in the Netherlands is that the 200 metres is pointless without the other 27 kilometres, whereas in Japan they are just convinced that it will work. We could apply a far more gradual approach to our water problems, by making incremental interventions that will ultimately produce a safe and dry Netherlands. 2.7.2.7 Public awareness One of the great things the Dutch could learn from the Japanese is how to create public awareness. Since both countries are each defined by their individual group-ism, the way how to create public awareness should be modelled by the Japanese example. Of course the Japanese have a head start with their long tradition of self-reliance of urban neighbourhoods. The availability of material concerning water projects in Japan is overwhelming. For the river projects there are visitor centres and even the new wastewater treatment plant


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Figure 2.48 Poster to make the inhabitants of Tokyo aware of the fact that fat spooled through the sink will end up as white balls in the water that will disturbed the wastewater treatment plant Source: Tokyo Metropolitan Government

Figure 2.49 Smaller used as flush water, the water can be used to wash hands after using the toilet Source: Fransje Hooimeijer

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in Tokyo has a sign where they show the whole world how many visitors they have had. They also have different promotional actions to inform the people of Tokyo how to handle their rubbish. Figure 2.48 shows a poster to make the inhabitants of Tokyo aware of the fact that fat spooled through the sink will end up as white balls in the water that will disturbed the wastewater treatment plant. Somehow the use of water and the ecological consequences of dirty water plus the energy that is needed to make it clean and available again is something the average Japanese person is aware of. Maybe because of their high technology such as the smart toilet that offers the water first for washing hands, and afterwards the same water can be used to flush.

Chapter 3

Historical floods with responding flood control Bianca STALENBERG 1 and Yoshito KIKUMORI 2 1

Section of Hydraulic Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands 2 River Division, National Institute for Land and Infrastructure Management, Tsukuba, Japan

3.1 INTRODUCTION This chapter focuses on floods in Japan which affect urban areas. The section on the Japanese river gives insight into the Japanese river system in comparison with the European Rhine river system. An overview of major historical floods shows the impact of natural hazards on Japan. The effects of a flood can be devastating. Flood control measures are therefore extremely necessary in Japan. An overview of Japanese flood control from ancient times until present time tells us that flooding has always been a problem. Therefore, Japan has a long history of flood control. The way flooding occurs is ambiguous. A distinction can be made in fluvial flooding and pluvial flooding. A fluvial flood is another definition for a river flood. A river flood occurs when river water covers other areas than the restricted river bed between the dikes. This happens for instance when the capacity of the river bed is insufficient. Water overflows the river dikes in combination with wave overtopping and inundates the adjacent districts. The dike itself can remain undamaged, but also erosion of the inner slope is possible. The river dikes can also fail due to several physical processes. Shearing of the dike is possible due to the occurring water pressure against the dike in combination with the increased water pressure in the subsoil. Sliding of the outer slope can be the case when the outside water level rapidly falls after high water. Piping is the result of seepage flow through the subsoil which triggers erosion behind the dike. Soil is borne along. Concerning special water retaining structures and hydraulic artifacts other failure mechanism are also of importance. This implies failure to close gates and the strength and stability of the upper structure, the foundation and subsoil (TAW, 1998). Pluvial flooding occurs due to direct rainfall and is a threat especially in urban areas. It is difficult to drain rainwater in urban areas. A large percentage of the surface is macadamized and is therefore impervious. Compared to urban areas, in rural areas water can easily seep into the ground. This phenomenon is referred to as the retention function. Additionally water can temporarily be stored in agricultural lands and ponds, the so-called retarding function. This system creates a runoff reduction; hence reduces the river discharge in the end. Furthermore the inflow speed is reduced preventing a large inflow in a short period of time that can overload the river system (Arakawa – Karyu River Office and MLIT, 2006). Urbanization misbalances these natural systems. Expansion of urban areas reduces the function of forests and paddy fields in retarding and infiltrating storm water (Nakao and Tanimoto, 1997). Increase

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Figure 3.1 Failure mechanisms of soil structures Source:TAW, 1998

in impervious earth cover, such as asphalt, concrete covering and storm sewers, also accelerates storm water runoff. This artificial system increases the river peak discharge and inundates low lying areas along the river course.

3.2 THE JAPANESE RIVERS 3.2.1 Geographical characteristics Japanese rivers differ greatly from the European rivers. In general, they are short, steep and flow rapidly down the mountains, across the plains and into the Pacific Ocean, the Sea of Japan or the Seto Inland Sea (Takahasi and Uitto, 2004). Japanese rivers have a short stream length; with a maximum of approximately 367 kilometer (Yoshimura, Omura et al., 2005). Japanese rivers have a steep gradient with an average of 0.44%. The Jyoganji River is one of the steepest rivers in Japan and has an average slope of 1.8% (Yoshimura, Omura et al. 2005). A result of this steepness is a high sediment transport, especially during fluvial flood events. Sediment transport from steep catchments mostly exceeds 1000 m3 km2 a1 with a maximum of 10,000 m3 km2 a1. Downstream riverbeds consist mostly of fine-grained alluvial plains (Yoshimura, Omura et al., 2005).

Historical floods with responding flood control

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Figure 3.2 A typical Japanese River Source: Bianca Stalenberg

3.2.2 River classification system River systems which are of importance for the national economy and people’s living are classified as A class river systems. Important parts of the 109 A class rivers, like urbanized areas, are managed by the central government; the other parts by the local government (Nakamura, et al., 2006). In 1989, A class rivers had a total length of approx. 86,798 km with a total catchment area of approx 239,912 km2 (River Bureau, 1990). Examples of an A class river system are the Tone River and the Ara River. Other river systems are classified as B class river systems which are managed by prefectural or municipal authorities. B class river systems counted in 1989 2,673 river systems with a total length of approx. 35,394 km and a total catchment area of approx. 107,692 km2 (River Bureau, 1990). 3.2.3 The European river Rhine The river Rhine has a length of 1,320 km. Compared to the Japanese rivers, this is a significant difference. However, in Europe the river Rhine is marked as only a medium-sized river (Boo de and Middelkoop, 1999). The Rhine starts in the Swiss Alps and crosses Germany before flowing through the Netherlands into the North Sea. The river feeds itself with rain water from nine different countries and melting water from the Swiss Alps. This differs from the Japanese rivers. Mean annual precipitation varies between about 600 mm in the lower downstream part and 2500 mm in the Alps (Asselman, 1997). Due to the melting water of about 150 glaciers more than 70 percent of the flow originates from the Swiss Alps during summer months. The lowest discharge is measured in the fall, when precipitation consists of not only rain but also

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Table 3.1 Comparison of a Japanese river with a European river

Source: River Bureau, 1990, Internationale Komission fuer die Hydrologie des Rheingebietes, 1993, Knepper, 2006

Figure 3.3 River IJssel; one of the Rhine branches Source: Bianca Stalenberg

snow. In return, this snow often gives extremely high discharges during spring time. The average suspended sediment concentration at the German-Dutch border is about 30 mg/l whereas a maximum concentration of 180 mg/l can be measured during peak discharge (Asselman, 1997). In the Netherlands, the Rhine branches into three branches which flow into the North Sea and the IJsselmeer. It is the most important river system of the Netherlands. It is an important waterway for inland navigation and provides water for drinking, agriculture and industry. The Rhine flows through the most densely populated areas of Western Europe and is one of the world’s busiest shipping routes (Brinke, 2005).

3.3 HISTORICAL FLOODS In Japan flooding and recession occur quickly. Peaks are less than a day. The maximum flood discharge is therefore relatively large compared to the small catchment


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areas. Fluvial floods seem to be inevitable. Furthermore, urbanization has triggered pluvial floods. Torrential rain runs off quickly along the impermeable pavements and inundates many homes. Japanese history proves this statement. This section gives an overview of the historical floods of Japan and their impact. 3.3.1 Major floods of the Meiji period (1868–1912) During the Late Meiji period several fluvial floods of the Arakawa River struck the area of Tokyo (Arakawa – Karyu River Office and MLIT, 2006). In 1896 approximately 655 homes and about 120 hectares of farmland were inundated. The flood of 1902 struck seven cities and villages, and left about 880 homes flooded. Tokyo was hit again by a flood in 1907. The area of Iwabuchi was totally inundated and resulted in shutting down the factories between Iwabuchi and Oji. The flood affected 180 cities and villages, and severely damaged crops, homes, embankments and bridges. The fluvial flood of 1910 was the most severe. The flood killed 369 people (including casualties in the Tone river area), destroyed or washed away 1,679 homes and flooded 270,000 homes. The total damage counted more than 120 million Yen (approximately 1 million US Dollar) (Arakawa – Karyu River Office and MLIT, 2006). 3.3.2 Major floods of the Taisho/Early Showa period (1912–1945) In the beginning of the Early Showa period, Tokyo was struck by another typhoon. The typhoon arrived in Tokyo on September 30 in the year 1917, and created recordbreaking high tides (Arakawa – Karyu River Office and MLIT, 2006). About 800,000 thousand households were flooded and more than 500 people were killed. In 1923 an earthquake caused serious damage. Embankments along several rivers broke due to the great Kanto earthquake. The earthquake took a total of 91,000 lives. These events show that both typhoons and earthquakes can have devastating effects on a country. 3.3.3 Major post World War II floods (1945–1973) After the end of the Second World War, Japan was hit by a series of major typhoons which took place until the end of the fifties. Almost every year many lives were lost. Typhoon Kathleen struck in 1947 and produced a record-breaking amount of rainfall in all the water systems north of Kanto. The typhoon caused several dike failures such as the massive dike failure along the Tone River at Kurihashi, only seven kilometers upstream from Tokyo, which resulted in an inundated area three kilometers wide and affected 300,000 people (Arakawa – Karyu River Office and MLIT, 2006). The resultant flood flow also affected Tokyo metropolitan area (River Bureau, 1990). The total affected area is estimated to be about 440 km2 in which about 600,000 people were affected and about 150,000 houses damaged. The total economic loss is estimated at about 100 billion Yen (approximately 838 million US Dollar) (Infrastructure Development Institute-Japan and Japan River Association). Heavy rainfall, caused by Typhoon Kanogawa in September 1958 is associated with the highest flood in the Tsurumi river basin and the Kanda river basin in terms of total rainfall and rainfall intensity. In the period September 25–September 27 a cumulative rainfall of 395 mm was measured in the upper region of the Tsurumi River. This was

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Table 3.2 Major floods in the period 1945–1959

Source: Arakawa – Karyu River Office and MLIT, 2006

the most severe rainfall observed since 1896. This heavy rainfall caused dike failure and flooding on both sides of the main stream and several tributaries. Hundreds of houses were flooded up to the second floor. It resulted in the complete destruction of 403 houses and left more than 835,000 houses damaged. Typhoon Kanogawa affected a total of 119,867 people (Nakao and Tanimoto, 1997). The Ise Bay Typhoon struck in September 1959 and caused the highest casualties of any postwar typhoon. At the Ise Bay the typhoon coincided with high tide which led to a level rise of 300 mm every ten minutes. A record high tide of 5.81 m was reported at Nagoya port which exceeded the height of the sea wall (Arakawa – Karyu River Office and MLIT, 2006). The hinterland was inundated with sea water. In June 1966 the Tsurumi river system and the Kanda river system were hit again by a typhoon. Typhoon no 4 caused serious flooding. The average two-day rainfall reached 307 mm in the Tsurumi river basin. The maximum discharge reached 1,000 m3/s. This was twice as high as the discharge capacity of the river itself. Approximately 17,160 houses were flooded. In 1972, Japan was flooded in the rainy season. Heavy rain fell from July 5 to July 13 (Takahasi and Uitto, 2004). The whole country suffered from significant flood damage that exceeded the figures of the Ise Bay typhoon of 1959. About 443 people died. 3.3.4 Major floods of the Heisei period (1989-present) Despite the major fluvial flood works, which were carried out since the beginning of the twentieth century, floods are still a major concern. Japan counted an average flood damage cost of 567 billion yen between 1994 and 2003 (approximately 4.7 billion US Dollar). This figure is the highest for any country worldwide (Nakamura, et al., 2006). The Kanda River remains a target for typhoons and severe rainfall. Several typhoons hit this area in the 1980s and again in 1993 the area was hit by a typhoon. The flooded area was limited to 132 hectares, but still more than 4,500 houses were flooded. Furthermore the entire JR railway system of Tokyo metropolitan was out of order (Ando and Takahasi, 1997). In September 2000, heavy rainfall in the Tokai district led to dike breaches on the Shinkawa River (Motoyoshi, Sato et al., 2004). The daily precipitation during this flood event was one third of the average annual rainfall (Ikeda, et al., 2005). Amongst other cities, Nagoya city was flooded. This is one of the three biggest metropolises in central Japan with a population of about two million people.


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More than 21,800 houses were damaged of which 98 houses totally collapsed. This event is known as the Tokai flood. Again, in 2004, Japan was hit by several strong typhoons. They killed a total of 215 people and caused serious economic damage. Furthermore, Japan had to endure heavy rain in July 2004 in the Niigata region (Ikeda, et al., 2005). Due to this heavy rainfall, embankments were partially destroyed and muddy floodwater entered the surrounding urban areas. More than 26,000 houses were inundated and fifteen people drowned.

3.4 HISTORY OF JAPANESE FLOOD CONTROL 3.4.1 Ancient times (River Bureau 1990) In ancient times people lived on the safe hilly areas; far away from the threat of fluvial floods. Gradually they recognized the advantages of living near rivers. Land along the rivers was fruitful and rivers were convenient for irrigation purposes. On the other hand, these areas were exposed to floods. This threat however, did not hold back the Japanese people to move to the more spacious lowlands. At start people moved to small streams but in time people also moved to larger streams and bigger rivers. They protected their land with drainage channels and dikes. These activities however did not prevent the regular inundation of irrigation land and homes. In 742 an act was adopted which allowed the Japanese who had reclaimed land to own it as their private property. This resulted in the growth of privately owned land and the foundation of feudal communities. 3.4.2 Sengoku period (1478–1602) (River Bureau 1990) In the sixteenth century the ancient feudal lords expanded their farm land in order to gain more economic power. People moved further downstream to the big rivers in the delta area. River improvement works, such as dike construction and channel digging, were executed to control the rivers. These improvements did become successful in some cases. For instance, the feudal lord Hideyoshi Toyotomi gave order for a channel relocation of the Kiso River in the Inuyama area and for the construction of a dike along the Yodo River in the region of present Osaka. Feudal lord Hohjo and his family constructed a dike along the Ara River in the Kanto region, near present Tokyo. 3.4.3 Edo period (1603–1867) (River Bureau 1990) The Edo period was a period characterized by economical and cultural development and an increasing population. Major progress in civil engineering was made (Nakamura, et al., 2006). To protect the Japanese people and its assets, ring dikes were constructed. Later ring dikes were connected and dikes along the main rivers were constructed. Due to the power of the feudal lords, who were under the supervision of Tokugawa Shogunate, the expansion of the cultivated land continued. It was not possible to protect the entire river basin (Takahasi, 2004). This was due to financial and technological constraints. Flood protection projects against fluvial floods were carried out selectively on major rivers which were of importance to the shogunate. As soon as Ieyasu Tokugawa moved to Edo, former Tokyo, in the beginning of the seventeenth

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Figure 3.4 Kiso River in the eighteenth century Source: River Bureau, 1990

century, he ordered the diversion of the Tone River to protect Edo. At that time the Tone River flew through the current Ara River and Edo River into Tokyo Bay. Two diversion works finally led the Tone River directly into the Pacific Ocean (this is described in chapter four). With the eastward diversion of the Tone River, the settlement Edo started a rapid development from a swampy village to a metropolitan, as we know Tokyo today (Nakamura, et al., 2006). It must be mentioned that Tokugawa Shogunate not only ordered flood protection works but also works for the improvement of navigation. Development of embankments, irrigation and navigation turned the large flood plains into useful paddy fields.


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3.4.4 Meiji period (1868–1912) During most of the Edo period scientific and technological activities were national orientated. Import of export of knowledge was prohibited. The Dutch, and to some extent the Portuguese, were the only connection with the western society. This trading relation had however been under a strict regime during large parts of the Edo period. In the beginning of the Meji period, Japan changed into a modern western democracy. Foreign experts were invited to facilitate the modernization of Japan (Nakamura, et al., 2006). The exclusive role of the Dutch ended, though close contacts between the two countries continued. Dutch engineers, such as Cornelis van Doorn and Johannis de Rijke played a key role in river engineering. They helped the Japanese with several river projects which were for navigation and irrigation purposes (River Bureau, 1990). River research and planning based on modern science and technology were first acquired from the Dutch (Takahasi, 2004). In 1885 Japan was struck by fluvial floods creating severe damages and the Meiji Government was pressed to construct river projects especially designed for flood control (Takahasi and Uitto, 2004). The floods of 1893 and 1896 became the motivation for the enactment of first River Law in 1896 (River Bureau, 1990). It declared the public ownership of rivers and river water and made a distinction in the responsibility of different parties. The River Law assigned the central government as the responsible party for flood control measures that demand large funds, high technology and nationwide planning. The local government was held responsible for ordinary flood management (Takeuchi, 2002). The main goal of this act was to save the alluvial plains in the midstream and downstream areas of rivers from flooding (Takahasi and Uitto, 2004). Flood control projects became, next to railroads, the most important infrastructure development in Japan. Under the River Law numerous flood control projects were undertaken on a large scale on the main rivers. The government constructed a continuous dike system and initiated major works for navigation and fluvial flood protection purposes. These works were welcomed by the Japanese people that were seen as a symbol of civilization’s progress. In 1896 the first large flood control projects were initiated on the Yodo river and the Chikugo river. Numerous projects were initiated on other rivers as well. For example the Arakawa floodway that was initiated after the flood disaster in 1910 and was finished in 1930. Due to these large scale river projects the frequency of flooding in river basins, especially in flood plains, decreased. The back side of these developments is the barrier which was built between the river and its residents (Takahasi, 2004). 3.4.5 Mid Showa period/Post World War II period (1945–1973) The Second World War gave Japan other priorities and flood control projects were left behind. During the war there was poor maintenance of dikes and channels . After the Second World War, Japan was attacked by a series of serious flood events (River Bureau, 1990). A wet climate with large typhoons and torrential storms in the period 1945–1960 had a lot of impact (Takeuchi, 2002). More than 1,000 people were killed nearly every year with a total of about 20,000 people in the entire period. Typhoon Makurazaki (1945) took 1,700 lives, typhoon Kathleen took another 1,930 lives and typhoon Isewan (1959) took 5,000 lives. In addition, the execution of the large scale river projects in the first half of the twentieth century had a down side. Torrential rain

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Figure 3.5 Plans for construction of Arakawa floodway Source: Arakawa – Karyu River Office and MLIT, 2006

was collected for quick discharge towards the sea or ocean. This was done for the entire catchment. The result was that the midstream and downstream flood discharges increased; even with the same amount of precipitation. This process led to frequent embankment failure in midstream and downstream areas (Takahasi, 2004). A large series of flood disasters eventually led to the enactment of the Flood Fighting Act in 1949 (Infrastructure Development Institute-Japan and Japan River Association). This act implied collaboration with meteorological sectors in order to develop systematic flood forecasting and early warnings. Furthermore flood hazard maps needed to be drawn up for specific rivers (Ikeda and Yoshitani, 2006). This Flood Fighting Act has been revised several times since the last decades. The period 1950–1970 is characterized by large economic growth (Takahasi, 2004). the downside of this rapid urbanization was the transformation of permeable paddy fields into impermeable landscapes which had an increase in the pluvial flood risk as result. Another development was the severe water pollution due to the industrialization along the rivers. Conversely, the water demand increased as a result of the industrialization and fast growing population. Water shortage spread through entire Japan. To meet this water demand a water recourses development plan was initiated with a focus on dam construction (Takahasi and Uitto, 2004). Dams were actively constructed in mainly the upper region of the river basins. Japan has the fourth highest dam density in the world. Only three of the 109 A class rivers flow without dams (Nakamura, et al., 2006).


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Within twenty years most rivers were constrained and polluted (Takeuchi, 2002). Their appearance became artificial. River ecosystems were destroyed, fauna disappeared and the river landscape lost its natural beauty (Takahasi and Uitto, 2004). This is especially noticeable in river cities, such as Tokyo. Rivers have been transformed from a green creek into a concrete sewage. Rivers were no longer used for recreational activities. All these developments contributed to draw up of the second River Law in 1964 (River Bureau, 1990). This new River Law was an institutional framework for flood control and water use (Infrastructure Development Institute-Japan and Japan River Association). It introduced integrated management of river systems and at the same time developed regulations relating to water utilization. With the rise in living standards, public perception on flood and drought management changed (Takahasi and Uitto, 2004). During the seventies flood events became rare and the Japanese population gained faith in governmental flood control technologies. However, in the event a flood produced serious damage, they felt betrayed by their government and held the government responsible for their flood damage (Takahasi, 2004). This can be illustrated by the following example. Torrential rain during the rainy season in 1972 caused 443 deaths and the total flood damage exceeded that of Typhoon Ise Bay in 1959. Many flood victims blamed the government and went to court to get compensation. Cases where affected people won lawsuits became more frequent and changed the perception of flood disasters of the general public. They started to demand more out of the flood control projects. 3.4.6 Late Showa period (1974–1988) As mentioned before, urbanization in the period of 1950–1970 changed the hydrological cycle radically and increased the flood risk, especially for pluvial floods. For example, the floods of 1977 in Nagasaki were a reaction to the extensive hillside development of urban areas. The floods were caused by a torrential rain of 180 mm/hour and took 375 lives (Takeuchi, 2002). In the period 1974–1976 three dike failures occurred at the major rivers Tama, Ishikari and Nagara (Kundzewicz and Takeuchi, 1999). The response of the government was the policy of Comprehensive flood management in 1977. This comprehensive approach combines the conventional river basin measures with innovative river basin measures focusing on retardation and retention, and damage mitigation measures (Takahasi and Uitto, 2004). At first, this approach was only limited to cities that experienced urban flood damages. However it became clear that all urban areas should be protected with this approach. Ten years later, in 1987, the River Council proposed a policy for protection from extreme floods to protect specific urban areas. These urban areas comprised of a concentration of important property and business functions. The policy is only applied for extreme floods which exceed the design levels of the regular flood protection measures (Takahasi and Uitto, 2004). An example within this new policy is the super levee. This dike has a very gentle inner slope on which urban rehabilitation is possible. The super levee has already been implemented on several locations in Tokyo and Osaka. 3.4.7 Heisei period (1989–present) Since the 1980s, recovering the river environment had become an important issue in river management. It became clear that the former river basin activities had deteriorated

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the ecology of a huge number of rivers. This was especially noticeable in urban river basins. A turning point in river management is seen in 1990. The government launched the initiative of ‘nature oriented river works’. The initiative conserved and improved the river corridors and their rich biodiversity. These developments led to a draw-up of a policy for improvement of river environment in 1995. This policy was drawn-up to protect the diversity of the habitat, to protect the hydrological cycle and to reestablish the relationship between rivers and the Japanese communities. These policy changes led to an amendment of the second River Law in 1997 (Takahasi and Uitto, 2004). The third River Law recognized that river projects were no longer only for flood control or water use functions, but that they also should satisfy ecological needs of plant and animal communities. They should conserve and if possible improve the environmental aspects of the river basin. All rivers should provide a healthy atmosphere which creates an open habitat for diverse plants and animals. Japanese inhabitants also demanded an attractive waterside for recreational activities. Rivers became an important component of the regional climate, landscape and culture (Infrastructure Development Institute-Japan and Japan River Association). Recent flood events show that serious flood damage is still difficult to prevent. Nowadays there is an enormous concentration of population and properties together with an increase of underground areas. Total urban flood disasters have increased significantly. This resulted in the Flood Fighting Act being revised in 2005. Most important revisions were the improvement of flood forecasting and the improvement of dissemination of flood information to the public, such as the use of flood hazard maps. The development of evacuation plans for underground areas was also a new aspect (Ikeda and Yoshitani, 2006).

3.5 COMPARISON WITH DUTCH FLOOD CONTROL The development of the Dutch territory can be described as a continuous dialogue between the powers of water and those of mankind. Protection against floods as well as the usage of water characterizes the Netherlands and its residents (Hooimeijer, et al., 2005). Similar to the Japanese situation, Dutch rivers attracted people because of their accessibility and their fertile soil. In ancient times, river dunes were very popular for settlements in the Netherlands. These river dunes were formed due to the morphological behavior of rivers (Ven and Driessen, 1995). The sand dunes were however not giving that much protection against fluvial flooding and settlements were regularly flooded. The sand dunes can be seen as the first protection against floods and as the forerunner of the currently known dike. The first dikes were built in the tenth century. These early flood defenses were local structures, upstream of the villages (Boo and Middelkoop, 1999). Quays were constructed transverse to the river and were meant to block the water flowing from upstream settlements. Like in Japan, the first flood defenses were private structures and built on a local scale. Unfortunately, these structures did not prevent a series of floods around 1200. This resulted in a closed dike system along the major Dutch rivers around 1300 (Ven and Driessen, 1995). A similar process can be seen in Japan in the beginning of the Edo period. In the Netherlands, this establishment did not mean that the cities were free from floods. Many dikes were still too low and too weak for a full protection of the area. Every winter this resulted in an inundated hinterland (Ven and Driessen, 1995).


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During the middle ages many Dutch cities flourished and protection against theft and other hostile activities was needed. Fortifications were built to protect these cities. The effect of such a development was that the sandbanks and dikes (temporarily) lost their function. The fortifications were built in such a way that the land outside the bulwarks could be inundated to protect the settlements against hostile attacks. The fortifications could therefore also function as a primary flood defense against water from more upstream situated lands. In some cities the course of the river was altered. These changes were mainly based on decisions made by local government. Until the eighteenth century these actions were taken without taking the total river system into account. It caused a poor state of the rivers and new measures were executed to turn this development. Around 1700 the first large measurement was executed: the construction of a new bifurcation point between the Waal and the Rhine. This bifurcation point led to a stabilization of the discharge division of the Rhine. When the Batavian Republic was established in 1795, the central government became responsible for water management care. Within the central government, one ministry was charged with the realization of water management. The construction, operation and maintenance of hydraulic structures of the central government were also the responsibility of this ministry. From this point on large river works were feasible such as the construction of channels, deepening of existing rivers and the construction of groins for the navigability of the rivers (Ven, 1993). Similar large scale river works were seen in Japan around this period. In 1874 the Fortification Act was proclaimed (Will, 2003). In most cities fortification was taken down which induced the restoration of the original sand dune, dike as flood protection whereas in other cities the quay wall was quite suitable for flood protection usage. Until the beginning of the twentieth century dike improvements were made after each breach. Dikes were designed for the worst-known-scenario with 0.5 m freeboard. Like in Japan serious flood events were seen as triggers to change the governmental

Figure 3.6 Room for the river measures Source: Flyer Handling water differently

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approach towards flood protection totally. The twentieth century with its industrial revolution and a fast increase in knowledge on countless topics gave the opportunity to make real changes. In the Netherlands, severe fluvial and storm surge floods of 1926 and 1953 showed that former flood control was not enough to prevent floods. The Delta Commission advised the implementation of a new system of protection based on probabilities. The Dutch Delta was divided into dike ring areas. The safety level differed per dike ring, depending on the population density and the economic value in a dike ring. It took several years before the recommendations of the Delta Commission were used to formulate the Flood Protection Act. This legislation was adopted in 1996. Every five years all fluvial and storm surge flood defenses are checked on their ability to answer the ongoing hydraulic boundary conditions. The hydraulic boundary conditions are those water levels and waves that have to be blocked safely by the flood defense. The hydraulic conditions change over time due to alterations in climate and morphology, and therefore have to be reassessed and reset every five years (Brinke and Bannink, 2004). Since the last two centuries many floodplains have been used for human activities and the economic value behind the dikes increased enormously the last decades (Project organisation: Room for the River, 2005). The enormous growth is especially noticeable since the 1950s. The Flood Protection Act incorporated an economic growth of circa two percent per year. However in the period 1953–2000 the economic growth has been significantly higher with averagely 3.8 percent per year (Brinke and Bannink, 2004). Since the beginning of 2006 an updated version of the Flood Protection Act is therefore operational. The added paragraph states that the efficiency and effects of the imposed safety levels have to be reported every ten years (Staatsblad, 1996). In the last decade the Dutch flood protection paradigm changed from ‘fighting the water’ to ‘living with water’ (Immink, 2005). The Netherlands was struck by extreme flood conditions during 1993 and 1995. About 250,000 people were evacuated and the River Meuse caused several floods (Project spankrachtstudie, 2002). The national government wanted to prevent such an event from happening again. Hence, the government aimed at sustainable safety and spatial quality. This reflection is incorporated in the current policy documents (such as the advice of the Commission Water management twenty-first century and the policy document Room for the River) and practically results in measures that give more room for the river. The main policy is to create more space for retaining, storing and draining of water in this specific order. This approach can also be seen in the Japanese comprehensive flood management policy in which the entire water cycle with storm water and river water is incorporated. The measures of the Room for the River policy ensure that the discharge can increase without an increasing water level. There is a shift on emphasis from traditional dike improvement towards spatial measures (Project organisation: Room for the River, 2005). These measures will ensure a sufficient safety level against fluvial flooding. At the same time it will give a positive contribution to the spatial quality of river landscape. Comparing the Netherlands and Japan on this matter, it is seen that both countries place importance on the quality of the river environment.

Chapter 4

The development of river management: Tone River Satoshi NAKAZAWA Department of History and Philosophy of Science, The University of Tokyo, Japan

The development of modern river management in Japan can be roughly outlined in three phases: (1) river channel improvement for flood protection, (2) construction of multipurpose dams for mediating conflicting priorities, (3) introduction of measures against extreme floods and for the improvement of river environment. It was a judging process consisting of problems posed by rivers and human reactions to them which were not always successful. The case of the Tone River provides for a good picture of that process.

4.1 RIVER AND WATER MANAGEMENT IN THE PRE-MODERN PERIOD In the Edo period (1603–1867), river works were conducted under the control of the shogunate. Flood control in that time depended primarily on local countermeasures. For example, embankments protecting the land of the Shogun were made higher than those of other lords [daimyos] on the other side of the river who were also forbidden to raise the embankments. In some cases, embankments were built around settlements, being quite removed from the river in expectation of inundation. Along the river embankments a few overflow points were planned in advance and wood zones were formed in order to reduce the impetus of the overflow. Furthermore, inhabitants of flood-prone regions had provisions for the worst such as evacuation mounds [mizuka], elevated shelters [mizuya] and emergency boats (Gasteren et al., 2000, – 100–120; The River Law, E-i-E-ii; Okuma, 1988, 17–18).

4.2 THE BEGINNING OF THE MODERN WATER MANAGEMENT IN JAPAN Modern water management in Japan began during the Meiji period (1868–1912) when a number of the Dutch civil engineers was invited to this country. In 1872 chief engineer, Cornelis van Doorn, placed the first water gauges in Japan at Sakai-machi by the Tone River and in Kema by the Yodo River (Takahashi, 1990b, 134). The visiting engineer made plans for the improvement of rivers and harbours throughout Japan. Activities of the Dutch engineers are often characterized as river improvement with a view to navigability [teisui koji]. Customarily in Japan, water management [chisui] is divided into two parts, i.e. flood protection [chisui in a narrow sense] and water utilization [risui]. The latter comprises works for irrigation, drinking-water supply, inland navigation etc. In particular, works intended for improvement of inland navigation are called

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- ]’. Conversely, works for flood protection are called ‘high‘low-water works [teisui koji water works [kosui koji]’ (Gasteren et al., 2000, 203–205; Matsuura, 1992, 26, 33). In the beginning of the modern period, the Japanese government made an enthusiastic effort to increase production and to foster industries under the slogan ‘a rich nation, strong soldiers’. During that period, inland navigation was of the greatest importance as a means of transportation. Therefore the central government actively took the initiative to improve rivers for navigation, while flood protection was deemed to be a task of local governments. It was a widely accepted custom at that time, though – not explicitly determined (Okuma, 1980, 112–114; Matsuura, 1992, 12–25; Nippon kagaku-gijutsu-shi taikei, 1970, 18; Tone-gawa Hyakunen-shi, 524, note 1). This situation gradually changed after the advent of the railways. After the first rail line between Tokyo and Yokohama was laid, a network of railways quickly formed. The government constantly and strongly supported this enterprise. By the end of the Meiji period, the total length of the railway system reached approximately 11,000 kilometers. However, railway expansion undermined the position of inland river navigation which was dependent on the weather and the condition of low water. The center of gravity in transportation shifted from inland navigation to travel by rail (Matsuura, 1992, 28–31; Gasteren et al., 2000, 88–89). Contrarily, demand for flood protection developed against the background of the progress of reclamation of marshy areas. In addition, in the early and middle Meiji period, floods frequented many parts of Japan. When the Imperial Diet was inaugurated in 1890, a large number of requests for flood protection were submitted. In 1896, the River Law, the fundamental law concerning the public works for river improvement, was finally enacted. The law required local governments to assume the primary responsibility for river works and maintenance as before, but it also stipulated that the national government should undertake a river improvement project in cases where the project had interprefectural effects or if the difficulty or the cost exceeded the capacity of the local government concerned. The result was that the central government launched actively into works for flood protection. Directly after the enactment of the River Law, flood protection works for three of the principal rivers in Japan began under the direct control of the Ministry of Interior. Furthermore, fourteen years later, following a nationwide flood in 1910, the Emergency Flood Control Committee was formed by an Imperial order. The committee framed a First-phase Flood Control Plan and recommended increasing the number of rivers to be improved through – national projects to 65 (Okuma, 1988, 141–142; The River Law, E-ii-E-iii).

4.3

THE TONE RIVER IN THE PRE-MODERN ERA

- is one of the greatest rivers in Japan, running through The Tone River, or Bando- Taro, the Kanto plain (Figure 4.1). The plain, where Tokyo is located, is the largest in Japan. The total surface area of the Kanto plain is 32,000 km2, only slightly smaller than the total surface area of Netherlands (36,000 km2). Presently, the mainstream of the Tone River flows from the mountainous inland to the far north of Tokyo into the Pacific Ocean at Choshi, Chiba. The river basin 2 amounts to 16,000 km , the largest in Japan (Koide, 1972, 8–12). However, it was not so from the outset. Historical documents indicate that, prior to the modern era, the main river flowed into the Tokyo Bay (Figure 4.2).

The development of river management: Tone River

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Figure 4.1 Relief map of the Kanto Plain Source: Maarten Slooves

Figure 4.2 Estimated river basins 1600 Source: Maarten Slooves

Since Tokugawa Ieyasu moved in 1590 to Edo (presently Tokyo) and then later in 1603 established his shogunate, the Tone River underwent various artificial modifications. Finally, by cutting a new channel, it was connected to another river called Hitachi River that originally belonged to a different basin. Although the precise purpose of this great earthwork is not yet known with certainty, it is very likely that promotion of inland navigation was initially aimed at in order to improve the transportation of commodities from the hinterland to Edo. For Edo, then no more than an underdeveloped fishing port, it was sine qua non to grow into an important economic center comparable to older cities in western Japan such as Kyoto and Osaka (Koide, 1972, – 44–62; Okuma, 1981, 38–50). The development of Edo as a water city is described in greater detail in Chapter 2. Thus, a system of waterways came into existence that connected the northeast area of Japan to the Kanto region. A navigation route from the basin of the Kitakami River

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to the basin of the Tone River via Choshi was established. The route was connected to Edo via the Edo River, a large branch of the Tone River that splits off about forty kilometers to the north of Edo and flows into the Tokyo Bay to the east of the city – (Okuma, 1988, 108–111). The Tone River served as the trunk of that network throughout the Edo period (1603–1867). The principle of water management in the Tone River at that time was established by the Ina family who served the Tokugawa shogunate. In order to mitigate flooding they adopted soft measures that tolerated inundations to some extent. For example, they left a bottleneck between Sakamaki and Setoi in the upper Tone River so that flooding and overflow from the river channel would be hindered there from running downstream. Thus, the discharge in the middle and lower stream is supposed to have been limited considerably. The Sakamaki-Setoi bottleneck can justly be regarded as the pivotal anti-flooding measure of the Inas. This system seems to have functioned rea– sonably during the early and middle stages of the Edo period (Okuma, 1988, 112–115). The situation changed drastically in the end of the eighteenth century. In 1783, Mount Asama erupted and the descent of volcanic ash caused the riverbed to rise along the Tone River. Thereafter, inundations occurred more frequently all over the river region. The system implemented by the Inas was disturbed. At approximately that time, groynes were constructed at the upper mouth of the Edo River. The purpose of this construction was supposedly the protection of Edo against the floodwater of the Tone River. Because of complaints from the residents upstream, a convention was established that the river breadth at that point should be kept at least about 32.7 m. From then on it appeared that more water began to flow into the lower Tone River by flood– – ing and embankments there burst more frequently (Okuma, 1981, 63–98 and Okuma 1988, 115–120). Since then, the course of the management of the Tone River kept varying until the end of the Tokugawa shogunate (Figure 4.3).

Figure 4.3 1867 Source: Maarten Slooves


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4.4 THE BEGINNING OF THE MODERN ERA OF RIVER IMPROVEMENT IN THE TONE RIVER As mentioned previously, Dutch engineers were engaged with the Tone River since just after their arrival. Following the establishment of the water gauge at Sakai-machi, Isaac Lindo, a graduate of the Koninklijke Militaire Academie (Royal Military Academy) in Breda, took the level along the Tone River and established the original bench-mark for Japanese topographic maps. On the basis of this survey, he submitted a report ‘Rindo Nihon chisui no setsu [a report on water management in Japan by - 1928), in which he Lindo]’in 1873 (reproduced in Tonegawa kaishu- enkaku ko, proposed to return the floodwater of the Tone River to the Tokyo Bay, making the Edo – River the mainstream (Gasteren et al., 2000, 153; Okuma, 1981, 109–111). However, thirteen years later, when another Dutch engineer, Anthonie Rouwenhorst Mulder, drew up a master plan for the Tone River (A.Th.L. Rouwenhorst Mulder, ‘Tonegawa (Tsumanuma yori umi ni itaru) kaishu- keikakusho [an improvement plan for the Tone River from Tsumanuma to the sea], reproduced in Kurihara, 1957a and Kurihara 1957b), the idea to expand the Edo River was relegated to the background. Mulder states three objectives in his plan, namely, improvement of navigability, flood protection and reclamation of marshes. Concerning the first two points, he suggested the regularization of the river breadths. Although he proposed to remove the groynes at the upper mouth of the Edo River, the premise of his plan was that the distribution of floodwater between the Tone River and the Edo River should not be altered. This stipulation was probably consistent with the opinion of the concerned Japanese officials that Mulder would meet. Among other things, it is remarkable that Mulder recommended leaving a number of ponds along the lower Tone River intact as retard– ing basins (Okuma, 1981, 114–120. As for an overview of Mulder’s activities in Japan, see Gasteren et al., 2000, 290–311). Although Mulder’s plan was a rather rough outline and left much unsubstantiated, it presented a scheme to improve the entire Tone River from the upper stream to the estuary. According to this plan, the improvements would be implemented during the period from 1887 to 1905 on a budget of ¥4,077,215.657. In the work actually executed, it appears that emphasis was placed on maintenance of the minor bed and the - 1928, 32; [S. Kondo?], navigation channel (Tonegawa kaishu- enkaku ko, ‘Tonegawa Kosui Koji Keikaku Ikensho [advice on the plan for flood protection in the Tone – River]’, reproduced in Kurihara, 1957c and Kurihara, 1958; Okuma, 1981, 117). In the meantime, contrary to Lindo’s former proposal, the groynes at the upper mouth of the Edo River were reinforced and the river breadth at that point was considerably narrowed. While the breadth seems to have been 47 to 55 meter at the end of the Edo period, it was reduced to about 16 meter as a result of a series of constructions during the Meiji period in 1875, 1884, 1885, 1896 and 1898, respectively (Tonegawa kaishu– - 1928, 29; Okuma, enkaku ko, 1981, 123–125). Although contemporary sources suggest that this reinforcement was performed by initiatives from the Dutch engineers, it is implausible on grounds of their reports cited above. At that time, pollution of the basin of the Watarase River, an upper branch of the Tone River, produced a serious environmental problem. It was caused by toxic drainage – from a mine at Ashio and absorbed public attention. Okuma (1981, 125–129) suspects that the government was afraid that the polluted river water would enter Tokyo.

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In the same period as the improvements according to Mulder’s plan proceeded, floods repeatedly struck the area along the Tone River. The dissatisfaction of the residents took the form of fierce criticism against the so-called ‘Dutch techniques’. After the enactment of the River Law, improvements according to Mulder’s plan were discontinued in 1899 so that a new project, aimed principally at flood protection, was – launched in the following year (Okuma, 1981, 129–136).

4.5 THE FIRST IMPROVEMENT WORK OF THE TONE RIVER, 1900–1930 Instead of the plans of Lindo and Mulder, Japanese successors adopted a large-scale dredging and embanking scheme over the entire reach of the Tone River. The Tonegawa - [the Improvement Work of the Tone River] began in 1900 (Figure 4.4). In Kaishu- Koji the plan, design-flood discharge was fixed at 3750 m3/s in the upper stream. At this design-flood discharge, flooding was estimated to occur a few times during every ten years. For the Edo River, a discharge of approximately 970 m3/s was assigned and the idea to direct the main floodwater to the Edo River totally disappeared. Conversely, the plan that marshes along the lower stream should be separated by sluices from the mainstream in order to prevent backwater was practised. Consequently, all floodwater should now be disposed within the river channel as planned. The river was divided into three sections and construction works for each section started one after the other. The first and second sections, for which construction works were performed during 1900, 1909 and 1907–1930 respectively, primarily covered the lower stream. The third section included the middle and upper streams for which construction work occurred

Figure 4.4 Plan1900 Source: Maarten Slooves


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- 1928, 35–36; [S. Kond o?], during 1910–1930 (Tonegawa kaishu- enkaku ko, ‘Tonegawa Kosui Koji Keikaku Ikensho’ reproduced in Kurihara, 1957c and Kurihara, – - gaiyo, - 1928, 6–7; Okuma, 1958; Tonegawa kaishu- koji 1981, 137–152). However, on the 8th of August 1910, ten years after the work began, the Tone River was struck by a huge, unprecedented flood. The largest discharge in the upper stream was estimated at 7000 m3/s, nearly twice the design-flood discharge of the improvements under construction. The plan was revised and the design-flood discharge was increased to 5570 m3/s (Figure 4.5). The increment was to be coped with as follows. Firstly, because construction for the first term was already completed and that for the second term had already begun, a great deal of the increased discharge would be diverted to the Edo River. The assigned discharge was augmented from 970 to 2230 m3/s. Secondly, it was proposed to make the cross-section of the river as large as possible. Alterations during the third term were realized by (1) constructing retarding areas, (2) leaving the old river channel intact as much as possible such that the breadth between old embankments was wider than the standard, and (3) increasing the freeboard of dykes. The completed sections of the first and the second terms were managed only by raising dykes. Meanwhile, a large retarding basin was set up at the confluence of the Watarase River to the Tone River in order to prevent the influx of polluted flood discharge from the former to the latter, by compulsory purchase of Yanaka village. At the great cost of the village the basin was going to play a very important role in the management of the – Tone River thereafter (Tominaga, 1960; Okuma, 1981, 152–158). Thus, continuous embankments were built from upstream to downstream along the Tone River. What is remarkable is that the Sakamaki-Setoi bottleneck was broadened


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and its retarding function was lost. Although new retarding areas were provided, their capacity does not appear to have been comparable to the old bottleneck. In addition, while dischargeability in the upper stream was improved, that in the lower stream was not increased in proportion. Although the Edo River should receive the excess according to the plan, actual inflow was considerably limited by structures such as weirs and locks that replaced the old groynes. The disproportion between the upper and lower – streams appeared not long after the completion of the improvement work (Okuma, 1981, 158–173).

4.6 THE SECOND PLAN FOR THE IMPROVEMENT OF THE TONE RIVER During the period from 1935 to 1941, enormous floods visited the basin of the Tone River that tested the just accomplished improvement works. During the flood on the 26th of September 1935, brought by two successive typhoons, the discharge in the upper stream was estimated at more than 10,000 m3/s. Although the embankments along the main river escaped bursting, thanks to protecting activities, dykes along one tributary, the Kokai River, were broken in many places due to the backwater. Additionally, the high water level in the main river that lasted for many hours seriously hindered drainage from lakes and marshes along the lower stream and the surrounding areas remained under water for more than a month. Thus, weaknesses in the meas– ures taken against flooding in the lower stream were revealed (Okuma, 1988, 168–170). In response to this disaster, the Tonegawa Chisui Senmon Iinkai [the Special Committee for Water Management in the Tone River] was organized in order to establish a fundamental plan for flood protection. The main concern of the committee was to implement reinforcing measures in the sections previously improved during the first and the second terms of the former improvement work in which the freeboard of the embankments had not been increased while the retarding capacity had diminished by closing the marshes and lakes. The committee fixed the design-flood discharge at 10,000 m3/s and examined six draft plans. Raising dikes generally along the lower stream was considered to be infeasible for reasons including the weakness of the ground, the long duration of the high water level and the difficulty in draining the inner basin. The centerpiece of the plan that the committee finally adopted was the excavation of a floodway that would discharge 2,500 m3/s from Fusa on the Tone River directly into the Tokyo Bay. Expansion of the Edo River was discarded on grounds of its relatively high estimated costs. The opportunity to restore the Tone River to its – original watercourse was missed again (Okuma, 1981, 206–223). (Later it was evident that the initial estimation for the floodway had been too low. It was corrected from – ¥39.1 million in 1938 to ¥133.3 million in 1943. Okuma suggests the possibility that the expansion of the Edo River might be less expensive, even if inflation at that time was taken into account.) Just after the committee proposed the above mentioned plan, however, there was another move brought about from a different direction; it was a plan to utilize the Watarase retarding basin as a reservoir for the water supply in Tokyo. In this case, it would not be far from using that reservoir for flood retention. The retarding basin was projected to be capable of regulating 1,000 m3/s of the maximal discharge of the Tone


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River with the addition of some adequate facilities. Furthermore, if the overall discharge in the Edo River and the lower Tone River could be increased slightly, the discharge in the planned floodway would reduce to 1,000 m3/s. That discharge was considered to be small enough to be coped with by alternative measures. Thus, there emerged a plan to construct a flood control dam at Ikari, upstream of the Kinu River, instead of the floodway. In fact, the Ikari dam had already been planned around 1923 as a part of the improvement work for the Kinu River and came into effect in 1926. However, it was stopped in 1933 because of a couple of faults found in the dam site, together with a limited budget (Tominaga, 1957). Considering that the costs for the floodway had been underestimated, the plan for the dam was likely to be more economical. Yet, for various reasons, a decision was not reached. Not until two typhoons played havoc in 1938 was a definitive plan determined. The plan, the Tonegawa Zoho Keikaku [the Supplementary Plan for the Tone River], arranged to be executed since 1939, subsequently underwent minor modifications as a result of another typhoon in – 1941 (Okuma, 1981, 223–225). According to this plan, the design-flood discharge of 10,000 m3/s should be reduced by 500 m3/s due to the Watarase reservoir (Figure 4.6). The Edo River should assimilate 3,000 m3/s. The Tone Canal, constructed in 1890 as a shortcut of the navigation route according to the design by Mulder, was to be adapted for use as a diversion channel in order to direct 500 m3/s to the lower Edo River. The effective discharge from the Kinu River was to be maintained at 1,480 m3/s by two dams at Ikari and Kawamata. Two reservoirs near the mouth of the Kinu River should retain a total of 850 m3/s. The mouth of the Kokai River should be shifted downstream and its discharge was not to affect that in the main stream of the Tone River. As for the core of


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the entire plan, the discharge flowing through the Tonegawa Floodway was deter– mined to be 2,300 m3/s (Tominaga, 1966a, 1966b, 1966c; Okuma, 1988, 168–173). The Tonegawa Zoho Keikaku marked a new epoch in the history of the improvement of the Tone River. While the preceding plan was intended only for flooding that occurred several times per decade, the Tonegawa Zoho Keikaku established a thorough and integrated plan for flood protection in the entire Tone River for the first time, raising the design-flood discharge to 10,000 m3/s. The plan promised a real beginning of flood protection in the Tone River comparable to those in other major Japanese rivers. However, this plan was never accomplished primarily due to the out– break of World War II (Okuma, 1981, 246–250).

4.7 THE – INTRODUCTION OF THE CONCEPT OF KASUI TOSEI [RIVER WATER CONTROL] In the meantime, the emphasis in water management works shifted slightly. After inland navigation diminished, the most important user of river water was the agricultural sector. By the end of the Edo period, the minimal discharge during the dry seasons had nearly been exhausted in most of the rivers in Japan for use in irrigation canals. – Customary water rights were acknowledged (Okuma, 1988, 183). However, as the industrialization of Japan increased, demands for power generation or industrial use increased. Additionally, growing megalopolises, especially Tokyo, were about to drink up their own reservoirs. This tendency was enhanced during World War I when Japan evolved into a modern industrial nation, taking advantage of the vacuum that occurred in the supply for markets in East Asia because of the war. Subsequently, conflicts occurred among the various users of water (The River Law, E-iii; Yamauchi, 1962, 11–13). Thus, the idea of Kasui Tosei was born. Primarily, administrators and engineers of the Ministry of Interior were advocates for the idea. They introduced the concept of flood control by storing floodwater in dammed reservoirs and attempted to reconcile flood protection with other interests. The construction of multipurpose dams would serve them best. They were deeply influenced by similar projects in Europe and in the United States. Among others, activities of the Tennessee Valley Authority (TVA) made a great impression on the protagonists of River Water Control. Simultaneously, in order to adapt other projects to the Japanese situation, theories of earthquakeresistant design were also developed (Yamauchi, 1962, 18–24; Mononobe, 1925 and Mononobe 1928). - Iinkai [the Committee for the In 1938, the cabinet finally established the Kasui Tosei Control of River Water]. Under the lead of the Ministry of Interior, projects for that purpose were planned for seventeen large rivers, although most of them were not accomplished under the unfavorable circumstances during World War II (Yamauchi, 1962, 24–51; Matsuura, 1985).

4.8 THE APPEARANCE OF LARGE-SCALE MULTIPURPOSE DAMS The construction of large-scale dams was realized after the defeat of Japanese militarism. After the war, the General Headquarters of the U.S. Occupation Forces (GHQ)


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supervised all affairs concerning the economy, the society and the politics in Japan. Within the GHQ existed a Natural Resources Section of which the technical adviser was Professor Edward A. Ackerman of Chicago University. Subsequently to the end of the war, Ackerman remained in Japan for more than one year and studied natural resources in Japan and their uses. Finally, he made a comprehensive report concerning the resources in Japan. He also suggested that without colonies Japanese industry would recover to its status before the war only if its own natural resources were used efficiently. Emphasis was placed on the development of water resources (Yamauchi, 1962, 56; Kawakami, 1995, 66). Under the auspices of the GHQ, the Keizai Antei Honbu [the Economic Stabilization Board, Anpon] was established in 1946. After disorganization of the Ministry of Interior, the Anpon assumed the task of administering national development plans. The Shigen Iinkai [the Resources Board] was attached to the Anpon. That board was modeled after the National Resources Planning Board of the U.S. government that was established by President Franklin Roosevelt in order to promote New Deal policies. In 1950, the Comprehensive National Land Development Law was enacted in which comprehensive development of rivers played a central role (Kawakami, 1995, 65–67; Yamauchi, 1962, 51–55). From the latter half of the 1950s to the 1960s, a large number of multipurpose dams were constructed in the upper streams of the important rivers in Japan. Fifty-eight large-scale dams, higher than 30 meter, were constructed in 1946–1955, 174 in 1956–1965 and 199 in 1966–1975. The emphasis of the development was initially placed on electric power, then shifted to water resources. In order to meet new demands for river management, the River Law was totally revised in 1964 for the first time since its enactment in 1896. The appearance of large-scale multipurpose dams is characteristic of river water management in Japan in the latter half of the twentieth – century (Okuma, 1988, 181; Takahashi, 1990a, 152–159).

4.9 THE THIRD PLAN FOR THE IMPROVEMENT OF THE TONE RIVER USING MULTIPURPOSE DAMS Meanwhile, in 1947, two years after the defeat of Japan in World War II, a gigantic typhoon named Kathleen struck Japan and an unprecedented flood struck the Tone River once again. The maximal discharge in the upper river was estimated at – 17,000 m3/s (Okuma, 1981, 251–264). This cipher is astonishing, considering that the design discharge of the Rhine, which has a drainage basin more than ten times as large as that of the Tone River, is determined to be 16,000 m3/s at Lobith (Ven, 2004, 292–293). At that time, dykes burst near Kurihashi and the floodwater flowed through the eastern section of Saitama prefecture to inundate two wards of the Tokyo Metropolitan Government (Figure 4.7). Because of this inundation, 7.5 percent of the – population of Tokyo, i.e. about 380,000 inhabitants, suffered damage (Okuma, 1988, 173; Takahashi, 1971, 13–15). Thus, the Tonegawa Kaitei Kaishu- Keikaku [the Revised Plan for the Improvement of the Tone River] was designed (Figure 4.8). A number of multipurpose dams were projected to play an important role. The basic flood discharge was determined on the basis of the estimated discharge of 17,000 m3/s, of which 3,000 m3/s should be stored by dams in the upper tributaries. Of this plan, construction of multipurpose dams proceeded

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Figure 4.7 Inundated area 1947 Source: Maarten Slooves


steadily, whereas the construction of the Tonegawa Floodway failed to materialize – (Okuma, 1981, 268–281, 296–299, 321–340). The plan was revised again in 1980 in response to the estimated increase in the maximal flood discharge (Figure 4.9). In that plan, the design-flood discharge was augmented to 22,000 m3/s. In order to meet the increased discharge, the assignment of flow to the Edo River was augmented by 1,000 m3/s and the capacity of the upper


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dams was to be increased to 6,000 m3/s. However, specific sites for new dams were not established. Additionally, no indication exists that construction of the Tonegawa Floodway is about to begin as the planned site has now grown into a densely built-up – zone (Okuma, 1988, 175–180. See also postscript of this chapter).

4.10 REACTION AGAINST CHANNEL-CENTERED WATER MANAGEMENT AND REFLECTION ON THE RIVER ENVIRONMENT While the construction of multipurpose dams was steadily ongoing, a number of problems emerged that were rooted in the conventional methods of modern river improvements used since the Meiji period. Although the multipurpose dam was introduced as a new element, the principle of river improvement remained to discharge all floodwater into the river channel by regularizing the river breadth and raising embankments. The premise was that no floodwater should flow out of the channel while virtually no measures were considered against extreme floods larger than the design flood. However, a trend appeared in which peak flooding increased as the improvement of the river channel proceeded. Some experts considered this phenomenon to be a consequence of the improved dischargeability of the channel and the reduced inundation. Increased peak flooding presented a potentially fatal dilemma to modern river improvement. If current principles were maintained, the projects for raising dykes and expanding the channel would be endless. Concomitantly, rapid urbanization altered

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the form and distribution of land utilization in the river basin, which resulted in changes in flood runoff patterns that instigated new types of inundation in urban areas. In the 1970s, embankments successively burst along important rivers, such as the Tama River (1974), the Ishikari River (1975) and the Nagara River (1976). The number of cases increased in which flood victims accused the river administrator (Takahashi, 1964; Takahashi, 1971 and Takahashi, 1988, 25–30). Under these circumstances, the Minister of Construction consulted the River Council in 1976 after the burst in the Nagara River, caused by a disastrous typhoon The following year, the Council submitted an Interim Report on Policies for Comprehensive Flood Control Measures. In this report, they proposed measures such as restraints on flood and sediment discharge in the river as well as maintenance of the retention and detention functions of river basins in addition to conventional improvement works on the river channel. This report is considered to have marked a turning point from flood control centered on the improvement of the river channel to water management in the – entire river basin (Takahashi, 1988, 31–32; Okuma, 1988, 232–239). In addition, measures against extreme floods that exceed the design flood level were also introduced, on the basis of the River Council’s 1987 report titled Recommendations on Policies for Protection from Extreme Floods, in order to protect urban areas in which property and important business functions are concentrated. One example of the new measures is the so-called ‘super levees’. These are embankments that have an enormously wide levee crown. In so doing, they reinforce the resistance against overflow, while areas – created on the crown can be used as sites for various urban facilities (Okuma, 1988, 239–246; Takahashi, 1990b, 139–141). The super levees are further described in chapter 5. Meanwhile, in the 1970s the river environment emerged as an issue concerning river improvement. Although various river-related problems, such as water pollution, had already presented serious social problems, legal and administrative countermeasures were almost limited to regulations against water pollution and had little influence on the river improvement planning. Flood protection and stabilization of water supply were regarded as the most important objectives in river management during the 1950s and 1960s. However, because of the two oil crises, the economical growth slowed down in the 1970 and the increase of water demand for urban population stagnated. Water demand from the industrial sector decreased as a consequence of technical innovations and the change of industrial structure. In addition, repeated inundations damaged public confidence in the ordinary measures for flood protection. All in all, these factors seemed to have raised consciousness of the river environment (Takahashi, 1988, 28–34; Suzuki, 1995). In 1980, the Kasen kankyo- kanri kihon keikaku [the basic plan for river environment administration] was established, followed by the Kasen kankyo- kanri no arikata ni tsuite no toshin [the report on the desirable method of river environment administration] in the next year. On the basis of these reports, administrative plans for the preservation of the river environment were framed and model projects were initiated. In 1990, the Tashizengata kawazukuri suishin ni tsuite no tsutatsu [the notification on the promotion of creating close-to-nature rivers] was published (Matsuzaki and Tamai, 1997). In 1996, the River Council submitted a report titled 21 seiki no shakai wo - o- ni tsuite [on the basic direction of tenboshita kongo no kasenseibi no kihonteki hok


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Figure 4.10 2000 Source: Maarten Slooves

future river improvement with a view to 21st-century society]. On the basis of this report, the following year the River Law was revised for the second time. The revised River Law embraced the consequences of the developments since 1964 (Matsuzaki and Tamai, 1997; Sato, 1997). The major alterations are summarized as follows (Sato, 1997): Firstly, ‘improvement and reservation of the river environment’ was added to the goals of the Law. Secondly, the planning scheme for river management was revised and the river management plan was roughly divided into two constituents, the Fundamental River Management Policy and the River Improvement Plan. While the former is an abstract long-term plan determined from the scientific and technological point of view, the latter is a concrete, short-term plan that reflected opinions of local communities. In addition to opinions of local residents, the input of experts other than river engineers can be sought. Thirdly, in recognition of the traditional technique of forming woods along the embankments in order to prevent bursting due to overflow, the river administrator is entitled to form and maintain ‘fluvial wood zones’ as river administration facilities. The revised Law can be considered to be a step in the direction of departure from channel-centered river management.

4.11 CONCLUSION Since the beginning of the modern period, river management in Japan has been performed under the influence of diverse interests. Sometimes conflicts in river management are described as those between chisui versus risui, or security versus benefit. However, it seems more suitable to say that security has always existed as the primary goal of river management while its phenotypes were under the influence of the then prevailing interests. Thus, continuous embankments were a technological expression in a period when interest in reclamation and wet rice culture prevailed, whereas flood protection using multipurpose dams was a product of the necessity to coordinate a variety of new interests in a modern industrialized society.

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Currently, the circumstances of rivers are changing again. Agriculture has declined. Hydroelectric generation has decreased in importance due to the development of alternative energy sources and water consumption in the industry has been economized using new techniques. The growth of the urban population has become stagnant. Revision of the River Law reflected the new situation. The ideal adopted in the new River Law has already had certain consequences. There are measures against extreme floods ongoing in relatively small rivers in urban areas such as making small retentions of parks or constructing underground reservoirs. In addition, so-called ‘close-to-nature’ river improvement is continuing on several minor rivers. Nonetheless, profound revision of plans for great rivers has not yet appeared. For example, although difficulties are evident in the construction of dams and the floodway in the plan for Tone River, no alternative has been adopted yet (Figure 4.10). After the first decade since the revision of the River Law in 1997, it is still unclear if the revised Law will bring about a fundamental reorganisation in the river management as a genuine turning point in the history of the modern river management in Japan. The course of water management still seems to be fluctuating between the old principle and the new ideal.

POSTSCRIPT The improvement plan of the Tone River was further revised in 2006. In this new plan the shelved Tonegawa Floodway has been abandoned. A discharge of 1000 m3/s, instead of 3000 m3/s for the floodway, has been assigned to the Inba pond, a part of the Tone River system which has been separated by sluices during the first improvement work and now half reclaimed. The discharge will go further from the pond through former irrigation canals into the Tokyo Bay. The quota for the upstream dams has also been reduced from 6000 to 5500 m3/s. These reductions will be compensated by raising allocations for the Edo River and the main channel of the Tone River respectively from 6000 to 7000 m3/s and from 8000 to 9500 m3/s (River Bureau, – 2006; Okuma, 2007, 3005–308).

ACKNOWLEDGEMENT The content of this chapter first appeared as ‘The development of modern river management in Japan’ in Tijdschrift voor Waterstaatsgeschiedenis 16 (2007), 1, 34–45. I made a number of modifications in the original text in order to adapt it to the present volume. I thank the Vereniging voor Waterstaatsgeschiedenis for permitting the reprinting.

Chapter 5

Urban flood control on the rivers of Tokyo metropolitan Bianca STALENBERG 1 and Yoshito KIKUMORI 2 1

Section of Hydraulic Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands 2 River Division, National Institute for Land and Infrastructure Management, Tsukuba, Japan

5.1 INTRODUCTION This chapter focuses on urban flood control on the rivers of Tokyo Metropolitan. An example of a flood protection measure from the beginning of the twentieth century is the Arakawa floodway in Tokyo. This project was executed before the large urbanization of Tokyo in the second part of the twentieth century. However, due to large urbanization, space was no longer available for the execution of new large flood control measures such as floodways. It became inevitable for the government to alter their flood policy. The Japanese Government established the policy of Comprehensive Flood Management with the introduction of damage mitigation measures. Ten years later, the super levee was introduced in dense cities, like the Tokyo Metropolitan Area. The aim of this chapter is not only to give insight in the Japanese situation but also to compare it with the Dutch situation. This comparison shows similarities and differences in flood control measures and can be important for future flood policies in both countries.

5.2 ARAKAWA FLOODWAY 5.2.1 Introduction to the Ara river The Ara River (Arakawa) has its origin at Mount Kobushigatake which has a height of 2,475 meters above sea level (Arakawa – Karyu River Office and MLIT 2006). It has a total length of 173 km and a catchment area of 2.940 km2. The Arakawa River flows in the Kanto Plain, through Saitama Prefecture and Tokyo (Arakawa river website 2007). The first 41 kilometers flow through an area with mountains, 24 kilometers through basin land and about 108 kilometers through low-lying plains. The lower part of the Ara River flows through the Tokyo metropolitan area into Tokyo Bay. About 9.3 million people live in the Ara basin (Arakawa-Joryu River Management Office). It has the third largest population concentration among major rivers in Japan after the Tone River and the Yodo River. The total assets in the basin are estimated at 150 trillion Yen (approximately 1.3 trillion US Dollar), of which about 78 trillion Yen are located inside potential flooding areas (approximately 654 billion US Dollar) (Arakawa-Joryu River Management Office). The river is a major source for drinking water for the Saitama Prefecture and northern Tokyo. Ara River provides drinking water to 15 million people and further river water is used for irrigation. The annual

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Figure 5.1 Ara River: length and width Source: Arakawa river website, 2007

flow is characterized by a low river flow level in May and June when the intake of agricultural water starts and a large rise in rainy season and the typhoon season from July to October. 5.2.2 Historical Arakawa The first activities along the Arakawa were tracked back from the Jomon period (BC8000–BC200) (Arakawa – Karyu River Office and MLIT, 2006). In this period the

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earth’s atmosphere warmed and a large part of the Saitama Prefecture was inundated due to sea level rise. In the mid-Jomon period the temperature dropped and created many tidal marshes. This development stimulated rice cultivation in the Yayoi period (BC200–AD200). Paddy fields were constructed in the alluvial fan of the Arakawa. With the increase of the population in the Nara period (710–784) and Muromachi period (1333–1568), cultivated land and villages were also founded in the plains of the river catchment. These foundations were located in an area which was easily irrigated, but also flooded. The battle against floods began. At first people were mainly taking measures to prevent soil from being washed away. In time more skills and knowledge were obtained and the engineering technology developed (Arakawa – Karyu River Office and MLIT, 2006). New paddy fields could be constructed on the flood plains of the Arakawa which were very successful. Rivers were used for transport of the crops, thus river transport flourished in the Edo period (1603–1867). Prosperity increased and many cities grew. This urban development increased the demand for lumber and forest industry flourished. To secure a shipping route for timber, logged in the mountains, and the rice trade, the government began several works such as the construction of Kuge Canal near Kumagaya (Arakawa – Karyu River Office and MLIT, 2006). This led to an alteration of the river course. The Arakawa was now joined with the Wada-Yoshino-Iruma river course and would flow into Tokyo Bay via the Sumida River. These works increased the flood risk and triggered several flood control measures. The city Edo had a high priority in this matter and rural areas were flooded to protect the main capital. During the Meiji period (1868–1912) the government established an industrial zone near the mouth of the Sumida River (Arakawa – Karyu River Office and MLIT, 2006). This zone was expanded and other factories were constructed at the turn of the century. Banning floods became an urgent matter for the city that was now called Tokyo. The inundations, which were allowed in the former paddy fields, were unacceptable in the newly built industrial areas. In 1896 a river law was adopted which centralized the control of the major rivers. In combination with several flood events, this led to a large scale construction of embankments and flood control channels, such as the Arakawa floodway (Arakawa – Karyu River Office and MLIT, 2006). In this period river transport declined due to the development of railway transport. After the Second World War urbanization along the lower Arakawa increased tremendously and the environment changed from paddy fields into large residential districts. The industrial areas also expanded. Water shortage became a real problem; especially with the introduction of flushing toilets (Arakawa – Karyu River Office and MLIT, 2006). This shortage was solved by the construction of the Musashi Canal which provided a part of Tokyo with water from the Tone River. At the same time the Arakawa became seriously polluted which was worst in the Sumida River. Domestic waste water and industrial waste water were to blame. Fish could not survive and the river produced bad odors. The construction of sewage systems in the 1970s improved the quality of the Arakawa water (Arakawa – Karyu River Office and MLIT 2006). Furthermore the Water Pollution Law was adopted in 1970. At this moment in time the water quality is still poor in several tributaries so further improvement is needed.

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5.2.3 The flood of 1910 During the Meiji period the threat of flood remained and furthermore the damage rate increased due to accelerated urban growth. At first improvements were executed on a local scale but they did not prevent floods along the Arakawa. Local governments were lobbying for better flood control which was looked into after the large flood of 1910. Large amounts of rain fell steadily from the beginning of August in 1910. Total rainfall recorded in Naguri, Saitama prefecture was 1,216 mm (Arakawa – Karyu River Office and MLIT, 2006). The river dimensions were too small for such an amount of precipitation and overflow of the embankments all along the Arakawa was the result. Dikes failed in many places; not only in the lowlands in the Tone, Nakagawa and Arakawa basins, but virtually the entire downtown area of Tokyo turning it into an enormous muddy area. It took two weeks for the flood level to subside. Transport and communication networks broke down and railway services were suspended for 7 to 10 days (Arakawa – Joryu River Management Office). The flood killed 369 people (including casualties in the Tone river area), destroyed or washed away 1,679 homes and flooded 270,000 homes. The total damage counted more than 120 million Yen (approximately 1 million US Dollars). This figure is equivalent to 4.2% of the gross national income at that time. The national government responded to this devastating event with the construction of a channel which would protect Tokyo from further fluvial flood damage (Arakawa – Karyu River Office and MLIT, 2006). This project involved construction of a floodgate at Iwabuchi and a massive diversion channel, which is called the Arakawa floodway. 5.2.4 Principles of a floodway A floodway or a bypass is an artificial channel which is connected on both ends to the main river course or is creating an additional branch which flows into the sea. The aim is to increase the discharge capacity of the river which will lead to a reduction of the upstream discharge (Project spankrachtstudie, 2002). This will lead to a reduction of the water level. Dikes are necessary on each bank of the floodway. The scale of the influence is determined by the cross-section, length and the gradient of the floodway. The dimensions of the inlet structures are also important. A floodway can be used temporarily but can also be used as a permanent side channel. In the first case the channel bed can be used for other activities during normal conditions, such as agriculture. The type of activities is of course depending on the frequency of the active use of the floodway. In the second case water is flowing through the floodway permanently. The height difference between the normal water level and the crest height of the dike gives the main river course an additional discharge capacity during flood conditions. 5.2.5 Specifications of the Arakawa floodway The Arakawa floodway is a massive diversion channel which lowers the water level on the Sumida River during flood conditions. The floodway has a length of 22 km and a width that varies between 445 m at the bifurcation point and 588 m at Tokyo Bay (Arakawa – Karyu River Office and MLIT, 2006). It is designed for a maximum discharge of 3,340 m3/s. The bifurcation point is realized with the construction of the


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Figure 5.2 Principles of a floodway Source: Project spankrachtstudie, 2002

Iwabuchi floodgate. Downstream of the Iwabuchi floodgate the Ara River was renamed into the Sumida River (Arakawa river website, 2007). During flood conditions the floodgate is closed and flood water is diverted towards the Arakawa floodway. The objective was to protect the lower parts of Tokyo in which 5 million were living against fluvial flooding. However, not everybody was eager to see the floodway being constructed as about 1,098 hectares of land needed to be procured and therefore about 1,300 households had to be relocated. The dislocated population feared finding new employment. Furthermore, people who remained in the area and lived between the Sumida River and the new floodway feared worse flooding. The project was started in 1911 with the procurement of the 1,098 hectares. Temporary railroad tracks were constructed for the steam powered material which dug the channel. The excavated soil was used for the construction of the embankments. The channel was dredged to its final depth after it was filled with water. The construction of the floodway took a total of 20 years and was finished in 1930. About 3.1 million people were needed for the construction of the floodway. The total costs of the project were 31.4 million Yen (approximately 263 thousand US Dollars). A project of similar scale today would cost close to 230 billion Yen (approximately 1.9 billion US Dollars). This figure does not contain the reinforcement of embankments (Arakawa – Karyu River Office and MLIT, 2006).

5.3 THE EFFECT OF URBANIZATION Many years of flood control efforts, in the field of both fluvial flooding and pluvial flooding, have reduced the total inundated area, but the flood damage has hardly decreased (Infrastructure Development Institute-Japan and Japan River Association). In fact, the annual death toll has remained at a number of several hundreds for a long time (Kundzewicz and Takeuchi, 1999). The reason is that the population and its properties continued to be located in flood hazard areas. Further there has been rapid urbanization

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Figure 5.3 Current course of the Arakawa floodway Source: Arakawa – Karyu River Office and MLIT, 2006

in many parts of the country, particularly in the Tokyo metropolitan area (Nakamura, et al., 2006). This process of urbanization has reduced the function of forests and paddy fields retention for stormwater (Nakao and Tanimoto, 1997). Due to scarcity of space buildings and infrastructure were constructed on ponds. Ponds were no longer used for retarding stormwater. The increase in impervious earth cover, such as asphalt, concrete covering and storm sewers, accelerated stormwater runoff. The pluvial flood frequency has increased in the newly developed urbanized areas. It has become a major urban problem since the 1960s (Ando and Takahasi, 1997). Japanese urbanization reflected the rapid industrialization since the mid-1950s. The population figure increased from 84 million during the fifties to nearly 128 million in 2005 (Statistics Bureau of Japan, 2006). The Japanese population which was working


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Table 5.1 Delta cities in Japan and The Netherlands Osaka Population Total area Inundation area

Kyoto 2.6 million 208 km2 94%

Population Total area Inundation area

Rotterdam 1.5 million 610 km2 73%

Population Total area Inundation area

0.6 million 319 km2 40%

Source: Statistics Bureau of Japan 2006, River Bureau 1990, Centre for Research and Statistics 2006

in the first economic sector, like agriculture, forestry and fishery, reduced from more than 50% at the end of the Second World War to 17% in 1970 (Kundzewicz and Takeuchi, 1999). More than 50% of the population and more than 70% of the nation’s assets are concentrated in the flood plains (Nakamura, et al., 2006). About 80 percent of the villages and cities have to deal with water damage caused by floods. If another Typhoon Kathleen hits Japan today, the direct damage would be about 150 times more as the damage caused in 1947 (Infrastructure Development Institute-Japan and Japan River Association). The original residents of flatland areas knew for many generations where it was relatively safe to live and in which areas the rivers would flood the hinterland during extreme discharges. Damage caused by inundation was not compensated. However, land is cheap in the inundation areas and many new houses are built on such land. Some of these houses are adjusted in such a way that the ground floor can be flooded without too much damage. Nevertheless most of them are not resiliently built. The use of underground areas is much more widespread nowadays than was at the beginning of the twenty first century. Dike failure has led to a new serious threat: disastrous flooding of underground areas (Arakawa – Karyu River Office and MLIT, 2006). For example, during a flood that inundated the Hakata district of Fukuoka (Kyushu island) in 1999, people were unable to escape from the basements of buildings. Many people drowned. During the Tokai Flood of September 2000, the subway services in Nagoya were temporary shut down. In case of a dike failure along the Ara River, the flood damage in Tokyo will be even more severe than in Fukuoka or Nagoya. Tokyo has an enormous and dense subway system with a high concentration of underground shopping malls. A simulation has shown that if an Arakawa dike near Kitasenju in Adachi Ward would breach, water would flow into the subway at Kitasenju station and reach Otemachi station in only two hours. 5.3.1 Focus on Tokyo The effect of industrialization is mostly noticeable in Tokyo. In 1920 Tokyo counted about 3.7 million residents. This figure has increased since then enormously to approximately 12.6 million residents in 2005 (Statistics Bureau of Japan, 2006). Tokyo has a population density of 5,748 per square kilometer. Comparison to the Netherlands shows that the main capital Amsterdam only counted 0.7 million people in 2006 (Statistics Bureau of the Netherlands, 2006). However, Amsterdam has a population density of 4,459 per square kilometer which is also rather high, compared to the rest of the Netherlands.

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Figure 5.4 Tokyo in 1909, 1954 and 1996 Source: Arakawa – Karyu River Office and MLIT, 2006

In response to the growing demand for housing in the Tokyo metropolitan area the residential areas are expanding towards the less elevated western region and the flood prone eastern area. The result is noticeable in the Naka river basin and the Ayase river basin. Here, the urbanized areas have increased enormously from 11% in 1965 to 43% in 1995 (Infrastructure Development Institute-Japan and Japan River Association). Similar development is seen in the Tsurumi river basin. It is close to Yokohama and within an hour’s travel from the centre of Tokyo. Until the 1960s, most of the basin was covered with forests and paddy fields. Its favorable geographical location triggered large scale urbanization including housing development projects. The urbanized areas increased from 20% to 80% in only 30 years (Nakao and Tanimoto, 1997). The population increased from 4,00,000 in 1958 to 1,840,000 in 2005. Nowadays the basin covers the Keihin Industrial Belt, the crowded urban area in the lower part of the basin and the boomtown in the hilly zone of the basin (Unno and Maeda, 2005). This urbanization caused various problems in the Tsurumi river basin. It disturbed water retention and retarding functions, increased the river discharge, shortened the duration of the flood peak and increased the flood peak. This resulted in a higher frequency of both fluvial and pluvial flood disasters. Focusing on the lower Arakawa a very dense concentration of population and property along its banks can be observed. The average population density for the entire Arakawa basin counts 3,400 people per square kilometer. Some areas even reach a density of 9,200 people per square kilometer where tremendous private assets as well as public functions are concentrated (Arakawa – Karyu River Office and MLIT, 2006). This is the highest population density of any A class river section in Japan. Embankment failure will cause widespread flooding and tremendous damage in the metropolitan area. Large parts of cities like Tokyo and Osaka are located below the flood level of their main rivers (River Bureau, 1990). These areas are former flat plains which were formed


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Figure 5.5 Position of rivers in Tokyo Source: Arakawa – Karyu River Office and MLIT, 2006

by sediment carried by rivers. By restricting the river course no new sediment is carried in these regions, thus creating a height difference. A dike breach will give water free access to a large area. An entire region will be flooded. Furthermore, a large area in Tokyo was affected by subsidence. Due to the immense increase in the population the demand for water has also strongly increased. Part of this need was satisfied by the use of ground water that was initiated around the beginning of the twentieth century. However, this exploitation of ground water caused subsidence. Nowadays, subsidence has almost completely stopped thanks to the restriction on the use of ground water. Nevertheless, about 124 km2 of Tokyo (about 20% of the wards of Tokyo) experienced a subsidence of more than 4.5 meters. This area is located lower than the high tide in Tokyo Bay. Furthermore, about 32 km2 of this area is also located lower than the ocean surface at low tide (Arakawa – Karyu River Office and MLIT, 2006). 5.3.2 Urbanization in the Netherlands During the last two centuries the population of the Netherlands has grown by about 750 percent. This huge increase can be ascribed to several factors: high birth rates, low mortality rates and a positive balance of migration. High birth rates were, among other things, the result of urbanization. Furthermore cities grew significantly due to several agricultural crises that drove the population towards the city. This led to a new problem (Hoogenberk, 1980). Several cities such as Nijmegen and Arnhem were suffering from the spatial limitation of the fortification. Many cities built new houses on every empty spot they could find within the bulwark without much planning or structure. In 1874 the Fortification Act was proclaimed that regulated which fortifications had to be maintained and strengthened, and which fortifications could be taken down (Will, 2003). River cities were officially allowed to demolish their fortification. The canals which were part of the fortification were mostly transformed into large roads. Industrialization had introduced transport by train, tram and motor vehicles. From the end of the nineteenth century, traffic and transport by water was largely replaced by those new types of transportation. This led a transformation of more canals and singels into traffic roads and train tracks. These actions resulted in a drastic decrease of surface water and storm water storage suffered from this development.

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Since 1950 the river cities have grown substantially. The Dutch population has rapidly grown from ten million to sixteen million since 1953. In the same period the net national product has increased from ten billion to 345 billion (Brinke and Bannink, 2004). At first the expansion was needed to cope with the population growth, but soon there were many additional houses required. Less people lived together in one house. At the same time the houses became bigger and the number of rooms per house increased. The process of urbanization in the Netherlands led to similar consequences as in Japan. Cities expanded thus rural surfaces decreased. Runoff control for the pluvial flood control became of bigger importance. Furthermore the amount of assets, the population rate and economic value of the urban areas increased. The consequences of both types of flooding became much higher. To maintain the same safety level, many dikes and other flood control structures needed to be improved.

5.4 COMPREHENSIVE FLOOD MANAGEMENT Comprehensive flood management is a combination of river improvement, runoff control and damage mitigation measures, this tackles fluvial flooding as well as pluvial flooding (Infrastructure Development Institute-Japan and Japan River Association). It contains both conventional measures and innovative measures. Special attention is giving to flood retardation and retention. A new aspect in the Japanese flood management is the use of damage mitigation measures. River improvement decreases the risk of a fluvial flood and implies river bed improvement and the construction or improvement of structures like dikes, detention basins and floodways. River bed improvement can be carried out by for instance deepening of the river bed, lowering of the groins or dike relocation. Excavation of the river is done to increase the flow capacity within the embankments and to lower the

Figure 5.6 Concept of Comprehensive flood management Source: Arakawa – Karyu River Office, 2004


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water level. Dike improvements give the river more space in the vertical direction to discharge additional flood water. Detention basins increase the flow capacity downstream by storage of flood water. Floodways create branches of the main stream thus increasing the flow capacity. Dams are still used for storage of flood water. These structures reduce the quantity of flood flow to be transported downstream and therefore lower the flood level. Additionally, dams are of course also used for water recourses management. Runoff control decreases the risk of a pluvial flood and implies the preservation and enhancement of the retention and retarding functions in the river basin. The conservation of nature and the control of landfill are important in this matter. The macadamization of the surface, e.g. with tiles or asphalt, must be guarded. A solution which enables further urbanization is the use of a permeable pavement. The construction of ponds and regulation reservoirs contribute to increase of the retarding capacity of the area. Innovative retarding basins in Japan are the mega buildings, such as stadiums, and sport fields, such as tennis courts. They are used for temporary storage. These measures of runoff control will be discussed in more detail in chapter 6. Flood proof buildings are a new aspect of the Comprehensive flood management. This implies the development of buildings that are highly resistant to floods. Houses on piles or houses with an elevated floor construction are applied in districts with a threat of inundation. On site storage of storm water on roofs or basements is an example of private participation in runoff control. The focus on damage mitigation measures in the field of pluvial and fluvial flood control is new. The Japanese already have a lot of experience with coping with natural hazards, especially in the field of earthquakes. Expertise from this field is adopted for flood control. One of the damage mitigation measures is the establishment of warning and evacuation systems. Information for this system is obtained with river patrols, CCTV cameras and with an optical fiber network. The dissemination of information among local residents is also of importance. Examples are the distribution of hazard maps, warnings through their mobile phones and display panels in public spaces. 5.4.1 River improvement: Detention basin Detention basins regulate the amount of water flowing into the river and prevent flooding (Infrastructure Development Institute-Japan and Japan River Association). It creates sufficient water storage during flood conditions thus reducing the water level downstream of the detention basin (Project spankrachtstudie, 2002). The basin is mostly surrounded by dikes. One section of these dikes is lowered to lead flood water into the basin, the inlet. When the flooding has ceased, water is drained back to the river, e.g. via a spillway. The capacity of the detention basin is determined by the surface area and the difference between the ground level inside the basin and the height of the inlet. The basin capacity needs to be large enough to prevent flooding downstream. An example of a detention basin is the Tsurumi multipurpose detention basin. The Tsurumi river is an urban river with a length of 42.5 km and a catchment area of 235 km2 (Nakao and Tanimoto, 1997). Its catchment is located in the central part of Tokyo metropolitan area, close to Yokohama and in short distance of Tokyo centre. Until the 1960s most of the basin was covered with forest and agriculture fields, but has been transformed into a large dwelling district. With easy access from the major

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Figure 5.7 Principles of a detention basin Source: Project Spankrachtstudie, 2002


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Figure 5.8 Tsurumi multipurpose detention basin Source: Arakawa – Karyu River Office, 2004

cities and favorable topographical conditions, the basin has been rapidly urbanized (Yoshimoto and Suetsugi, 1990). The percentage of urbanization has increased from 20 percent to 80 percent in only 40 years (Nakao and Tanimoto, 1997). The forest and agriculture fields have reduced tremendously. Stormwater run off accelerated due to the increase of paved areas. The peak discharge has nearly doubled since the early 1960s. In reaction to this development, the Tokyo Metropolitan Government and the city of Yokohama produced a master plan for an overflow location with multifunctional facilities for dealing with the peak discharge of the Tsurumi River. The Tsurumi multipurpose detention basin is seen as one of the core projects of the taken measures on the Tsurumi River. The basin is located in the Kozukue/Toriyama region. In the past, it has already served as a natural detention basin for the river. By upgrading its natural functions with some human engineering, it became possible to give protection against the dangers of flooding to the surrounding communities as well as the communities further down the river (Keihin Office of Rivers). The detention basin is designed to ensure a safety from a 150 year flood. This implies a flood which has a probability of occurrence of once in a 150 years. The basin is excavated deeper than the surrounding grounds and has a capacity of 3.9 million m3. The height difference of overflow dike compared to the surrounding dikes is three meters. A sewage gate will flow the detained water back, into the river. The overflow capacity has a maximum of 800 square metres a second, which includes the capacity of the river forelands and the other upstream overflow areas. In addition to flood control, the basin serves multiple purposes. It contains a sports venue, a recreation area and a park for local

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Figure 5.9 Flow Rate Distribution Source: Arakawa – Karyu River Office, 2004

residents (Keihin Office of Rivers). Most prominent is the International Stadium Yokohama. The stadium is designed for a total 70,000 visitors, number of spectators at the 2002 World Cup final, and is one of the eye catchers in the region. This structure has been built with high foundations to prevent damage when flood water flows into the basin. The primary roads inside the basin are constructed along embankments or are elevated. The Tsurumi multipurpose detention basin has been operational since 2003 (Keihin Office of Rivers). 5.4.2 River improvement: Artificial underground channel In largely urbanized areas space is scarce and the construction of a regular floodway is mostly impossible. In Japan, artificial underground channels are used to solve this problem. An artificial underground channel has similar principles as a floodway. The channel increases the discharge capacity of the main river course thus creating a lower water level of this main river (Project spankrachtstudie, 2002) resulting in less flooding. The channels don’t necessarily need to be connected on both ends to the same river. A connection channel between two river systems is also possible. This can be the case when one of the river systems has more buffer than the other one. Furthermore this measure is not only suitable for water level reduction on rivers but can also be used for runoff control. Stormwater is collected in underground pipes and transported towards the lower section or mouth of a particular river. A combination between these two is also possible as can been seen in Figure 5.11. In both cases the channels are constructed with huge pipes which have similar dimensions as subway pipes. An example of an artificial underground channel is the Metropolitan Outer Floodway. This channel is located near the city Kasukabe in the eastern Saitama Prefecture, which is about 30 kilometers north of Tokyo. The area between the Naka River and the Ayase River consists of many small rivers and has a dish-type topography


Figure 5.10 The river is allowed to overflow at the overflow location in the event of flooding Source: Arakawa – Karyu River Office, 2004

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Figure 5.11 Artificial underground channel Source: http://www.mlit.go.jp/river/paper/pdf_english/19.pdf

which tends to collect water (Inomata). During the last decades this region has been strongly urbanized (Wijers, 2006). The Metropolitan Outer Floodway is constructed to discharge a portion of the flood water from the Naka River, Kuramatsu River and Ohotoshi-no-furutone River to the Edo River (Kanto Regional Development Bureau). The result is that flood damage is reduced or is even eliminated in this region. The floodway is constructed at a depth of 50 meters. The pipes have a length of 6.3 km with an average outer diameter of 12 meters (Wijers, 2006). The structure consists of five shafts with each a diameter of 30 meters. Four of them are used to collect water from the different rivers and one is used for pumping water into the Edo River. The pumping station has a capacity of 200 m3/s. The project was completed in 2006 and protects a region of 440 thousand residents. 5.4.3 Damage mitigation measures: Dissemination of information It is important to realize that the technical flood protection measures are not a 100 percent effective. The structures are designed for a certain extreme flood event with a specific return period. However, more extreme weather conditions can of course occur. Furthermore, there is always a probability that the structures might fail. In such cases it is of utmost importance that the local residents can be warned in time. Additionally people need to be warned who are visiting and enjoying the river sight for leisure activities. Although rainfall can be very local, it can already cause a large difference in the discharge downstream. If those people are not warned in time they can be dragged along and children might even drown. Also navigation on the main rivers needs to be warned about approaching typhoons or severe rainfall. Hence, the Japanese government has developed several measures to inform its inhabitants. For instance, river information display panels are placed at bridges and sluice gates that inform vessels about approaching typhoons (Arakawa – Karyu River Office and MLIT, 2006). Display panels throughout the city and in front of railway, bus and metro stations provide information to local residents.


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These panels can of course be used during all sorts of emergencies and is not restricted to flood events. At home, people are informed through television with special broadcasts. Websites inform local residents about the current state of the rivers. Furthermore, live images of the river and charts of the amount of precipitation and water level are disseminated via the internet (Arakawa – Karyu River Office and MLIT, 2006). Additionally, the internet can be used by local residents to state their position during a flood event. People throughout Japan can access the website to check if their relatives or friends are unharmed. It is important that the Japanese people get familiar with these websites; hence they are stimulated to use them in their daily life as well. An example is the ARA website which gives information about the Arakawa floodway. People can send their ideas on recreational activities along the Ara River with photos to the Arakawa Mobile Club. This volunteer organization collects them and publishes them on the website. The website is visited by about five million people a year and can be seen as a success (Arakawa – Karyu River Office and MLIT, 2006). Another way to inform people about flood conditions is through their cell phones. This system allows users to automatically receive disaster prevention information if they register for this service in advance (Arakawa – Karyu River Office and MLIT, 2006). In case of a flood hazard, the standby screen transforms into the emergency screen and provides the user with information about water levels and meteorological information during flood conditions. This service has been tested in 2004 and is now operational. 5.4.4 The Dutch strategy Room for the river The Dutch strategy Room for the river is focusing on river improvement and runoff control, containing similar measures as the Japanese strategy Comprehensive flood management (Project organisation: Room for the River, 2005) (Project spankrachtstudie 2002). Two main goals of this strategy are the protection of the Netherlands against river floods up to a demanding level and the improvement of the spatial quality of the river landscape (Project organisation: Room for the River, 2005). These goals are realized by using mainly spatial measures. With these measures the river discharge can increase without an increasing water level. Dike improvements will only be executed on spots where spatial measures are technically or financially not applicable. The spatial measures are divided into three groups: retaining, storing and draining. Goal of the retaining measures is that water is retained in tributaries or in the river basin in such a way that the discharge of the main river is reduced. This can be realized by optimizing the discharge strategy of a city thus preventing discharge of domestic water and urban stormwater during critical periods. Additionally stormwater can be retained in cities using ponds, ditches and urban canals. Innovative measures, like the Experimental Sewer System are not yet implemented in the Dutch strategy. The Dutch do debate a lot about innovative urban water management, but up till today pilots like green roofs have been constructed on a very small scale. The second group of spatial measures focuses on storing. The application of temporary water storage decreases the flood discharge in the main river. This can be achieved by constructing detention areas inside the dike ring areas. In contrast to Japan, detention areas have not been implemented yet in the Netherlands. Due to the large river basin of the Rhine, very large detention basins are needed to be effective. An example of a detention area is Japan is the Tsurumi multipurpose detention basin.

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Figure 5.12 Retaining, storing and draining of water Source: Anders omgaan met water flyer Ministry of Transport and Water

In the strategy Room for the river several measures are formulated that stimulate the drainage capacity. One of these measures is deepening of the riverbed. This measure leads to a large discharge profile and can be realized by dredging of the main river course. Dredging is already regularly done to guarantee a certain depth for navigation. Additional dredging is therefore not a problem. Groins are normally used to fixate the deepest point of the river on a desired location for navigation purposes. They also protect the river shore by keeping the current out of this region. However, during flood conditions these groins can hinder the discharge by giving the river an extra roughness. Lowering of the groins can decrease this roughness. Looking at the floodplains two measures are possible. Floodplains in general create extra discharge capacity, especially during the seasons when heavy rainfall occurs. During high discharges the river uses these floodplains as extra discharge capacity and partly as extra storage capacity. Deepening of the floodplains will enhance these capacities. A more drastic measure is dike relocation which also enhances the capacity of the floodplain. It can create a larger effect than deepening of the floodplains. A bypass is the most drastic measure which creates extra drainage capacity. A bypass is an artificial channel which is on both ends connected to the main river course. This measure provides the integration of flood protection with urban activities, natural landscapes or recreational areas. Project developers are very interested in this concept. In Japan this concept has proved to be effective. The Ara floodway is a nice example of a Japanese bypass.

5.5 SUPER LEVEE: A JAPANESE CONCEPT 5.5.1 Introduction In Tokyo metropolitan, a large population, valuable assets and the core functions of social and economic activities are concentrated (Arakawa – Karyu River Office and MLIT, 2006). Especially fluvial floods with dike breaches can cause severe damage. The impact


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Figure 5.13 Conventional dike and super levee Source: Arakawa – Karyu River Office and MLIT, 2006

will be enormously. In an area where natural hazards like typhoons and earthquakes are part of everyday life, the consequences of a breach along the conventional dikes are too high. The typhoons of the second part of the twentieth century and their destructive force exceeded everybody’s expectations. In 1987, this resulted in a policy for protection from extreme floods that was applicable on highly urbanized areas (Takahasi and Uitto, 2004). Extreme floods are floods that exceed the design levels of regular flood protection measures. This new policy raised the safety degree of flood control to a new level. The concept of a super levee is designed especially for extreme events in a highly dense urban area. Conventional dikes are transformed into super levees. It will reduce the probability of a super flood disaster and thus reducing the risk of such an event. Additionally super levees are integrated with city plans of the regional government (Arakawa – Karyu River Office and MLIT, 2006). This will lead to an added urban value of the region. 5.5.2 Specifications of a super levee A super levee is a river embankment with a broad width which can withstand even overflow, so that destruction can be prevented. Main difference to a conventional dike is the width; a super levee has a mild slope of 1:30 (Arakawa – Karyu River Office and MLIT, 2006). In other words, a super levee with a height of 10 meters will have a width of about 300 meters. Furthermore, the toe has been reinforced with a concrete slab and a steel sheet pile. The River Act states that a super levee must resist extreme flood discharges which results in a flood level higher than the design water level for which the high standard levees are designed for.

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A super levee is resistant to earthquakes, overflow and seepage (Arakawa – Karyu River Office and MLIT, 2006). The resistance to earthquakes is one of the most important characteristics of a super levee. A super levee consists of soil that resists liquefaction and slippage during earthquakes. The soft ground of the conventional dike is improved and the grade of its slope is reduced (Arakawa – Karyu River Office and MLIT, 2006). A combination of an exceeding water level and waves leads to the phenomena of overflow and wave overtopping. With both phenomena water flows over the crest and wave forces hit the crest and inner slope (TAW, 2001). Water infiltrates the dike and wave forces attack the top layer. Looking at a conventional dike, infiltration can eventually lead to sliding of the top layer and finally lead to failure of the entire dike. Wave attacks speed up this process. The construction of a super levee will prevent dike failure due to overflow and wave overtopping in most cases. The mild slope of the super levee prevents sliding of the top layer. Furthermore, the waves loose their energy gradually and do not hit the inner slope with large forces. The great width of the super levee also reduces seepage (Arakawa – Karyu River Office and MLIT, 2006). The saturation line of a super levee is much longer than of a conventional dike. Stability loss through internal erosion can therefore be prevented. The construction of a super levee cannot be efficiently undertaken solely as a river project; they have a great impact on the surrounding district. Super levee projects are therefore implemented in conjunction with urban redevelopment, land rezoning projects or other urban planning. A conventional dike is a mainly a mono-functional object on which sometimes a road is constructed. Building on top of a conventional dike is restricted. Additionally, improvement of a dike does not only mean heightening but also broadening of the dike. People and assets need to move. This is not desirable. The concept of a super levee takes those whishes into account. It provides usable land and space for dwellings (Arakawa – Karyu River Office and MLIT, 2006). A conventional dike is transformed into a super levee by heightening of the crest and by broadening of especially the inner slope with 1:30. In Tokyo a lot of people own a small piece of land. The process of dispossessing will take a lifetime and is highly money consuming. The ownership of the properties on which the super levee has been built, remains therefore unchanged (Arakawa – Karyu River Office and MLIT, 2006). Living on the inner slope of the super levee is therefore permitted. A super levee is therefore not only interesting for its technical specifications but also desirable from an urban planning point of view. The concept is based on incorporating both the needs of flood control and the interests of the inhabitants (Takahasi and Uitto, 2004). Added value is created through the restored accessibility of the river. The steep slope of the conventional dike prevents easy access (Arakawa – Karyu River Office and MLIT, 2006). The dike is mainly a barrier between the local residents and the river. The outer slope of a super levee is gentler than the outer slope of conventional dike. Moreover, the gentle inner slope, in combination open recreational spaces at crest level provides an open view towards the river smoothly (Infrastructure Development Institute-Japan and Japan River Association). Contact with the river is restored. 5.5.3 Super levees in Tokyo Super levees can be found along two rivers in Tokyo: the Ara River and the Sumida River. As stated before, the flood control projects of the Ara River were formerly based on a


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Figure 5.14 Super levees along the Sumida River and Ara River Source: Bianca Stalenberg

policy of Comprehensive flood management. Due to the extreme typhoons which struck Japan, super levees were added to this policy on the Ara River and Sumida River. Goal is to construct super levees along the lower part of the Ara River with a total length of 30 km. This is executed through small projects of about 200–300 meter at a time. This long process is due to the participation of many landowners and the municipality. Urban redevelopment is taken as point of departure in order to make the super levee feasible. MLIT works therefore closely together with the Spatial Planning Department of Tokyo Metropolitan Government who negotiates with the landowners behind the former conventional dike. The landowners can choose if they want to be bought out and move to another district or that they can return and live in a different home. Along the Ara River several parts of the embankment are already transformed into super levees. The difference is striking. In the previous situation the conventional dike was a large barrier between the river and the residents behind the dike. The dike was covered with bricks and concrete. However, today the super levee is integrated with a public park. The outer slope gives awareness of the fact that the park is part of the flood defense and is less a barrier than before. The park is attractive for people of all ages. It emphasizes the spaciousness of a natural environment. The super levees along the Sumida River have a different and more urban appearance. An example is the Okawabata river city. It is an urban development complex of 7,500 m2 with housing, park, cultural facilities and is built on one of the early super levees of the Sumida River (Arakawa – Karyu River Office 2005). This project was part of the Tokyo Metropolitan Government’s Okawabata Redevelopment Concept, which was launched in 1984 (Takenaka Corporation, 2000).

5.6 CONCLUSION Both countries have applied similar approaches of fluvial and pluvial flood control throughout the centuries. This is remarkable due to the differences in geographical location and meteorological conditions. Japan counts 200 volcanoes and more than 70% of Japan is covered with mountains. The Netherlands however is a rather flat country of which the highest point is only 322.5 meters above mean sea level. Japan is situated in the East monsoon region and is affected by 30 typhoons a year. In large contrast, the Netherlands is situated in Western Europe and does not experience any monsoon seasons or typhoons. The average precipitation in the wettest month is only 80 millimeters.

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In ancient times both populations were drawn towards rivers. Natural sand dunes gave the people some sort of protection against floods. In Japan, as well as in the Netherlands, primitive dikes were connected into a closed dike system. As time moved on, knowledge about river systems developed. The first large river work in the Netherlands was the construction of a new bifurcation point between the River Waal and the River Rhine in the beginning of the eighteenth century. The alteration of the Tone River in the beginning of the seventeenth century and the alteration of the Arakawa River course in the nineteenth century are examples of huge river works in Japan. These river works were not only executed for flood reasons but also for navigation purposes. Trade was very important in both countries and vessels were widely used for transportation. Until the twentieth century, scientific and technological activities were national orientated. In the beginning of the twentieth century, Japan opened its doors and introduced Western modern science and technology into its country. Dutch engineers, such as Cornelis Van Doorn and Johannis de Rijke helped the Japanese with several river projects. Flood disasters mostly trigger the improvement of the flood protection system. This behavior is seen in every country which has to endure floods. The twentieth century was marked with two historical floods; the flood of 1953 in the Netherlands and the flood of 1947 in Japan. Both floods resulted in the enactment of flood protection acts. In Japan the Flood Protection Act was adopted in 1949. The new Dutch flood policy was already operative in the 1960s but it took until 1996 before the Flood Protection Act was adopted. The large urbanization since the 1950s increased the economic value of both countries enormously. Due to the large population growth, water shortage spread through entire Japan. To meet this water demand a water recourses development plan was initiated with a focus on dam construction. Additionally dams were used for flood control. In the Netherlands, dams would not be effective due to the geographical location. The Netherlands is a rather flat country with very few hills. Another result of the large urbanization was the expansion of urban areas which led to lack of space for the improvement of flood protection structures. This developed resulted in two policies: the Japanese Comprehensive flood management policy in 1977 and the Dutch Room for the river policy in 1997. Both strategies tackled fluvial floods and pluvial floods. The Dutch policy Room for the river strived at sufficient flood control with additional value to the river landscape. The Japanese third River Law also focuses on environment. River measures should conserve and if possible improve the environmental aspects of the river basin. The measures within the policy Room for the river are similar to the Japanese Comprehensive flood management measures. Examples are floodways, detention areas, retarding canals and ponds. Innovative measures, like the Experimental Sewer System with permeable pavements, are not yet implemented in the Dutch strategy. This is one of the few differences in both flood control strategies. Exchange of knowledge can be very useful. Japan has a long history in coping with natural hazards. Experiences with earthquakes are used for flood control. For example, the Japanese concept of a very broad dike, the super levee, is constructed in highly urbanized areas to prevent breaches due to earthquakes. There is no real threat of earthquakes in the Netherlands. The need to develop a dike or other flood structures which are resistant to earthquakes is therefore


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not present. The use of damage mitigation measures for fluvial and pluvial flood control is also derived from the experience on earthquakes. These measures are part of the policy of Comprehensive flood management and are greatly developed since 1977. Evacuation maps, billboards, broadcasts on television and the internet, and a mobile phones warning service are a few examples. In the Netherlands we are far behind on these types of measures. Since recently a website is available which informs the Dutch inhabitants what to do in case of a hazard and how you can prevent damage to your home (http://www.crisis.nl). Evacuation maps are not yet available to the public. On this topic, cooperation between Japan and the Netherlands would be very effective.

Chapter 6

Stormwater management and multi source water supply in Japan: Innovative approaches to reduce vulnerability Rutger de GRAAF 1 and Jun MATSUSHITA 2 1

Section of Water Resources, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands 2 Shibaura Institute of Technology, Environmental Systems Division, Ecological Infrastructure, Tokyo, Japan

6.1 INTRODUCTION This chapter first presents the historic development of urban water systems in Japan. Subsequently the vulnerability framework is introduced, which is used to describe two components of Japanese urban water systems, water supply and stormwater management. The city of Tokyo is used as an example. Finally, implementation of these measures by government or private initiatives is discussed and a comparison is made with the Netherlands.

6.1.1 Historic overview of development of Japanese Urban Water Infrastructure The historic overview of Japan’s urban water system is described extensively by Matsushita (2007) and in chapter 2. In the economic reconstruction period after World War II, large investments were made to enable rapid industrial development. Examples are: multi-purpose dams, powerlines, water infrastructure and transportation infrastructure. Subsequently, an enormous population shift to the urban areas occurred and countermeasures against pollution and uncontrolled urbanization were urgently needed. Because in Japan, urban planning was lacking, government initiatives had to be supplemented by private initiatives or legalized ‘cause-pay-principle’ to off-set weak governance. Regulations were introduced to demand polluters and/or developers to install on-site type facilities at their cost. Herein, basin management systems were introduced together with private initiatives to supplement public works effectively through boosting on-site-type systems installation for flood control, pollution control and water demand control. In the years after the oil crisis, reduction of ever increasing consumption of energy and water resources was needed to make Japan less susceptible against resources rich countries and, as a result, to stimulate successfully eco industries and clean production technologies in Japan. At present, Japan has to deal with international commitment for greenhouse gas reduction, thus trying hard to create eco friendly urban system models based on public participation schemes.

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6.2 THEORETICAL FRAMEWORK Vulnerability is often defined as the sensitivity of a systems exposure to shocks, stresses and disturbances, or the degree to which a system is susceptible to adverse effects (White, 1974; IPCC, 2001; Turner et al., 2003; Leurs, 2005), or the degree to which a system or unit is likely to experience harm from perturbations or stresses (Schiller et al., 2001). The system under consideration can be a community or region. The vulnerability concept is widely used in studies on risks and natural hazards and often also includes social and political dimensions. Stress and disturbances on a system can be both exogenous and endogenous, ranging from changes in the environment to changes in society. Some vulnerability approaches consider threats from both inside and outside the considered system, as well as the capacity of the considered system to cope with these threats. Moreover, they consider coupled human-environment systems or the reflexive relation between human society and the environment, instead of only human systems and environmental threats (Fraser et al., 2003; Turner et al., 2003; Leurs, 2005). In the risk glossary of United Nations University, Thywissen (2006) concludes: “vulnerability is a dynamic, intrinsic feature of any community (or household, region, state, infrastructure or any other element at risk) that comprises a multitude of components. The extent to which it is revealed is determined by the severity of the event.” Vulnerability can be considered as a combination of four components: threshold capacity, coping capacity, recovery capacity and adapting capacity (De Graaf et al., 2007). Table 6.1 illustrates the four capacities framework. 6.2.1 Threshold capacity Threshold capacity is the ability of a society to build up a threshold against variation in order to prevent damage. In flood risk management, examples are building river dikes and increasing flow capacity to set a threshold against high river flow. In case of water supply, examples are constructing storage reservoirs to increase damage threshold in case of droughts. The objective of building threshold capacity is prevention of damage. The time horizon lies in the past; past disaster experiences of society are the guiding principle to determine the height of the threshold. In the Netherlands, for instance, for ages dikes were constructed that had the same height as the highest experienced flood. The dimensions of a water resources reservoir are determined by historic droughts and water use levels. As a result, the uncertainty of the height of the threshold is relatively

Table 6.1 Description of type, hazard frequency, time orientation, uncertainty and responsibility of the four components of the vulnerability framework

Stormwater management and multi source water supply in Japan

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low. The ability of a society to build, operate and maintain threshold capacity is determined by its social, institutional, technical and economic abilities. 6.2.2 Coping capacity Coping capacity is the capacity of society to reduce damage in case of a disturbance that exceeds the damage threshold. For flood management coping capacity of society is determined by the presence of effective emergency and evacuation plans, the availability of damage reducing measures, a communication plan to create risk awareness among residents, and a clear organizational structure and responsibility for disaster management. For water supply, the availability of emergency and backup water facilities that can be used in case of droughts and disasters, are important determinants of coping capacity. The objective of developing coping capacity is reduction of damage. The time orientation is instantaneous, because in case of emergencies, only ‘here and now’ is important. The uncertainty is low because the magnitude of the hazard is clear at the time society has to deal with it. Also for coping capacity the ability of a society to build, operate and maintain it is determined by its social, institutional, technical and economic abilities. 6.2.3 Recovery capacity Recovery capacity is the third component and refers to the capacity of a society to recover to the same or an equivalent state as before the emergency. For flood control, it is the capacity of a flooded area to reconstruct buildings, infrastructure and dikes. For water supply, it is the capacity to achieve a functioning water supply and sanitation system again. The objective of developing and increasing recovery capacity is to quickly and effectively respond after a disaster. The time horizon is instantaneous right after the disaster but will change gradually towards a focus on the future. Although economical damage estimates may be difficult, the uncertainty of the hazard magnitude will be relatively low compared to possible future hazards because the effects will still be noticeable. The economic capacity of the country to finance the reconstruction determines the recovery success to a large extent. However, institutional ability and technical knowledge are also important. A society that is able to recover from impacts of hazards will be less vulnerable for these hazards. Recovery time may range from weeks to decades, depending on the spatial scale and disaster magnitude. Recovering from the Katrina hurricane in New Orleans will probably take years. 6.2.4 Adaptive capacity Adaptive capacity is the capacity of a nation, a community living in a river basin, or even the world to cope with, and adjust to uncertain future developments and catastrophic not frequently occurring disturbances like extreme floods and severe droughts. Therefore the time orientation lies in the future. Although a system may be functioning well at present, human and environmental developments, both from inside or outside the considered system, can put a system under strain and threaten its future functioning. Examples are climate change, population growth, and urbanization. For flood control, the problem of adapting to uncertain future developments can be illustrated by an example of land use. Although future risks from river or sea floods are unknown, land use decisions that determine future vulnerability are presently being taken. For water supply, a good example is salt water intrusion. The sea level and river

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discharge in 2050 are unknown; hence also the future problem of salt water intrusion in deltas is unknown. However, decisions to construct inlets for drinking water production points in this delta are currently being made. The objective of developing adaptive capacity is to anticipate on future developments and impacts by constructing a robust living and working environment. The uncertainty of the nature and magnitude of future hazards and impacts is high and the frequency of occurrence is low, which is also illustrated in Figure 6.1. The capacity to adapt to these uncertain developments also determines the vulnerability of a system. Although the exact size and nature of changes are unknown, solutions will have to be developed for longer time horizons and financial and spatial reservations to allow for adaptations will have to be made. The IPCC (2001) has made a list of categories of determinants of the adaptive capacity of society: 1. 2. 3. 4. 5. 6. 7.

8.

The range of available technological options for adaptation. The availability of resources and their distribution across the population. The structure of critical institutions, the derivative allocation of decision-making authority, and the decision criteria that would be employed. The stock of human capital including education and personal security. The stock of social capital including the definition of property rights. The system’s access to risk spreading processes. The ability of decision-makers to manage information, the processes by which these decision-makers determine which information is credible, and the credibility of the decision-makers themselves. The public’s perceived attribution of the source of stress and the significance of exposure to its local manifestations.

The list points the large number of options available for society to increase its adaptive capacity, varying from technical options (1) to insurance policy (6) or communication strategies (8). The range and variety of possible adaptive options is large and the number of involved organizations in the adaptive capacity determinants is also large. Consequently, there is no clear picture about who is responsible for strengthening adaptive capacity. Moreover, there is societal disagreement about the developments, the problems, and the solutions that are relevant for adaptive capacity.

6.3 COMPLEX INTERACTIONS BETWEEN VULNERABILITY COMPONENTS It is a societal objective to become less vulnerable to all kinds of hazards, long term and short term. However, decreasing vulnerability is a complex task. Vulnerability components are highly connected. Consequently, increasing one vulnerability component often decreases one or more of the other components resulting in higher, rather than reduced vulnerability. The connection between vulnerability components is illustrated. Figure 6.1 presents a conceptual damage return period graph. As a result of dike construction or reservoir construction, environmental variations with low return periods will cause no damage. This is the threshold domain in Figure 6.1. Even if thresholds have been built, there will be some occasions when the threshold will be exceeded. Then, coping with hazard impacts and recovering from them is


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Figure 6.1 The four components and three domains of the vulnerability framework illustrated by a damage return period graph.The three domains are interrelated, changes in one domain affect the other domains, resulting in an overall change in vulnerability Source: Rutger de Graaf

necessary. This is the coping and recovery domain in which damage reduction is the prime goal. Finally, there are very unlikely events with very high return periods where the expected damage is so extreme that recovery is neither feasible nor possible. We want to prevent these types of occasions by adapting. Therefore, this is the adaptive domain. Figure 6.1 illustrates that by increasing only the threshold domain, for instance by building higher and stronger dikes for flood control or by building reservoirs for water resources, the coping and recovery domain becomes smaller. However, these domains are important; by coping and recovering people become aware of risks. An approach that only focuses on increasing threshold capacity results in a system that is increasingly vulnerable to rarely occurring disasters. Disasters that cause damage will occur less frequently, but the ones that do occur will cause more damage. Consequently, for a complete vulnerability reducing strategy, attention should be paid to all components and domains of vulnerability. In the following sections, Japan’s strategies and measures to deal with pluvial flooding and droughts will be discussed using the 4 component vulnerability framework. A distinction is made between measures at a national level and measures at municipal level. The Table 6.2 summarizes these measures.

6.4 DEALING WITH STORMWATER: FOUR COMPONENTS TO REDUCE VULNERABILITY Chapter 1 of this book points the extreme geography and climate of Japan. Because of intensive rainfall, flooding occurs frequently. This problem has been intensified by the process of rapid urbanization that has been described in chapter 2. In addition, land subsidence due to over extraction of groundwater in the economic reconstruction

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Table 6.2 Overview of vulnerability decreasing measures for water supply and pluvial flood control classified according to the four components of vulnerability

period, even further increased the vulnerability of urban areas for flooding. The Tokyo lowland, for instance, is composed of deltaic lowland and reclaimed land. The original elevation of this plain is less than two meters. Subsidence in Tokyo had already started around 1900s because of exploitation of groundwater. During the reconstruction period after the war, groundwater use increased, until control of groundwater was taken in 1961 by introducing binding regulation. In the period to 1965, groundwater use decreased and extraction stopped all together in 1975. By then some parts had already subsided by four meters. This has created about 124 km2 of land that is lower than high tide in Tokyo Bay and 32 km2 lower than low tide. In such a situation, water has to be drained artificially in a polder system, similar to the Dutch water management system in the western part of the


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Figure 6.2a The process of land subsidence in Tokyo Source:Tokyo Metropolitan Government, 1994

country. Due to the combined effects of geography, climate, urbanization and land subsidence, the vulnerability of urban lowland areas to flooding is high in Japan. As a result, a wide variety of measures are applied to reduce the vulnerability of urban areas from stormwater induced flooding. As Figure 6.2 shows, these components can be classified according to the four components of vulnerability and subdivided in national and municipal categories. 6.4.1 Threshold capacity In order to reduce the vulnerability of urban areas from flooding resulting due to heavy rainstorms a number of measures have been taken to build threshold capacity, both on a national level and on a municipal level. On a national level, during the period of rapid urbanization, river capacity has been increased multiple times as has been described in chapter 4. In addition, artificial floodways such as the Arakawa river in Tokyo were built to process large floods. In the postwar reconstruction period of the 1940s and 1950s, multipurpose dams were built for flood control, water supply and hydro power. Rapid

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Figure 6.2b The process of land subsidence in Tokyo Source:Tokyo Metropolitan Government, 1994

urbanization limited the possibility for further river enlargements in urban areas. In 1977 the River Council, part of the Ministry of Construction, the present Ministry of Land, Infrastructure and Transport (MLIT), announced the implementation of comprehensive mitigation measures recommended for flood control. Rainwater storage and infiltration facilities had to be introduced in many places like school yards, parks, parking lots and individual houses. The government started to make budgets available for these on-site drainage retention works in 1983. The Association for Rainwater Storage and Infiltration Technology was established by MLIT (1991). It concentrated its activities to draft the technical standard for infiltration facilities and published the infiltration guideline in 1995. The River Council for river control proposed the necessity of a well-balanced water


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Figure 6.3 Location of the Naka and Ayase urban rivershed, the terrain level is lower than the river level, this is similar to Dutch urban polders Source: Ministry of Land, Infrastructure and Transportation, 2002

cycle in urban areas in 1996. Moreover, underground floodways were constructed to bypass floods that result from high intensity rainstorms. An example is the Metropolitan Outer Floodway in Tokyo (described in chapter 5 of this book) that has been built by the national government that was constructed to drain away water from the urban canals and rivers in the Naka and Ayase rivershed, located at a lower level than the Edo river. This situation has a striking similarity with the Dutch urban polders where water is also artificially drained from low-lying urban areas to main drainage canals or rivers. This underground floodway has a discharge pumping capacity of 200 m3/s. Next to measures on national level, on a municipal level centralized sewer infrastructure to prevent stormwater from causing damage was constructed. Similar to many cities in Europe and the United States, Tokyo implemented its first sewer system at the end of the nineteenth century. Construction of sewers started in 1884 when the brick lined Kanda Sewer was constructed. At first, only a few houses were directly attached to the sewerage. Moreover there were no policies concerning connection of houses to the system. In 1908, the Tokyo City Sewerage Plan led to a more organized situation. Until 1922, the sewerage was directly discharging the water towards the Tokyo Bay. The Mikawahima Sewer Treatment Plant started operation to treat waste water. In 1943, the Metropolitan Tokyo Government started with the collection of sewerage charges. The further advancement of treatment of wastewater starts in 1952, also a sludge treatment facility started in Shibaura in 1961 and in 1962 the Bureau of Sewerage of the Metropolitan Tokyo Government was formed. Two years later, the Tokyo Urban Sewerage Plan wass converted to cover a sewerage plan for all the 23 wards of the city. Four motives were important to start with the improvement of water quality: the shortage of sufficient water resources, the Olympic Games in Tokyo in 1964, the publication of the book ‘Silent Spring’ (1962) by Dr. Rachel Carson about DDT accumulation in food chains, and the world-wide notorious Minamata-disease. This disease

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made approximate 100,000 persons suffer from health problems due to the long-term intake of mercury-polluted fishes that was caused by heavy industrial pollution (Matsushita, 2007). The Industrial Pollution Control Law was enacted in 1965, which stipulated public announcement of water quality standard for the first time in designated waters to prevent industrial pollution. In addition, innovating multifunctional projects like the Ochiai Treatment Plant were developed. This is a park situated on top of the plant. The end of this period is marked by the start of the construction of Tama Regional Sewerage system in 1968. Despite all these measures, pluvial flooding occurred more frequently, due to rapid urbanization. This is also illustrated with the increase in runoff coefficient that increased from 0.3 in the beginning of the twentieth century towards 0.8 in 1994 (Kiguchi et al., 1994). Urban flooding and water quality problems resulting from combined sewer overflows (CSO’s) caused the shift from combined sewer systems, in which wastewater and stormwater are transported in one pipe, towards separated systems. In Japan, since the 1970’s only separated sewer systems have been constructed in which the stormwater is collected separately from wastewater. However in a city of Tokyo, a major part (70%) of the sewer system still consists of a combined sewer system. The sewer system is being gradually upgraded to process a rainfall intensity of 50 mm/hour. For this purpose a ‘New Quick Plan for Stormwater’ has been issued by the Tokyo Metropolitan Government that runs from 2004 to 2009. By increasing the sewer capacity, a threshold is built against a large proportion of precipitation events to prevent damage. In addition to centralized measures to prevent damage from stormwater, figure 6.4 shows a number of decentralized measures that are implemented. Examples are source control measures such as local retention, infiltration and storage facilities. Although stormwater infiltration can prevent damage by reducing stormwater flows in the urban environment, it serves multiple purposes. Examples are: groundwater replenishment, prevention of land subsidence, preventing salinity, securing water resources, river flow maintenance and pollution control (Fujita, 1997). Stormwater retention on private area is stimulated by the government with subsidies. 6.4.2 Coping capacity measures The Japanese physical and geographical characteristics result in a high risk profile for natural hazards, including pluvial flooding. Because this type of flooding can never be completely prevented, the Japanese have invested in measures that increase their coping capacity in case of flooding in addition to measures to prevent flooding. The measures to prevent flooding were discussed under the threshold capacity section. The purpose of increasing coping capacity is reducing damage if a flood occurs. In 1949, The Flood Fighting Act was established after a severe flood disaster that was caused by a series of typhoons. The amendment in 1955 added flood forecasting/warning and the Flood Fighting Act was given a flood fighting committee system in 1958. The immense damage caused by the Typhoon Ise-wan in 1959 was a turning point for disaster management, giving rise to a movement to plan and prepare a comprehensive disaster management system. In 1961, the Disaster Countermeasures Basic Act was enacted. Since then, the disaster management system has been improved and strengthened following the occurrence of large natural disasters and accidents. In 2001 the Flood Fighting Act got an expansion with regard to forecast floods and the power to


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Figure 6.4 Examples of Best Management Practices to improve the current combined sewer system in Tokyo under the New Quick Plan for improvements of the combined sewer system Source: Tokyo Metropolitan Government

designate preventive flood areas. Currently, in order to increase the capacity to cope with flooding, on a national level, Japan has established comprehensive flood mitigation system with composition of structural/non-structural measures. At a national level the following measures are taken to reduce damage (MLIT, 2005): ● ● ●

Establishment of an evacuation and warning system, Augmentation of flood fighting capacity, Publication of maps with historical flood data and flood prone areas,

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Encouragement of flood proof buildings, Dissemination of information among local residents.

In order to successfully implement these measures and involve stakeholders, river basins authorities have been established in heavily urbanized river basins. Dissemination of easy-to-understand flood maps to residents has received increasing attention over the last couple of years. Mass media, cellphones and internet are used to effectively communicate such information. It is expected that these measures will increase the coping capacity by increasing flood awareness among citizens. To promote private initiatives that reduce flood risks, the central government has established legal incentives such as the cause pay principle for urban development. In 1963, the New City Plan Act was established. It stipulated that developers should invest in infrastructure related to their development. The most recent incentive is the Countermeasures Act. For large private developments in heavily urbanized river basins, compensating measures have to be taken by the developer, such as ponds, retardation basins or infiltration facilities. This contributes to increased coping capacity of an urban area, in addition to preventing flooding. Coping capacity during flooding is further enhanced by the construction of elevated infrastructure and flood proof infrastructure. A number of national highways in Tokyo are elevated to enable transportation of relief goods and possible evacuation of residents during disasters. Subways are protected against flooding by flood gates and sluices are deliberately over dimensioned and designed to facilitate the entry of large ships into the city during and after a disaster. This contributes to the ability of society to reduce damage. At the municipality level, technical examples of coping capacity measures are: flood proofing of buildings, and emergency stormwater detention storage ponds. Social examples are measures to increase risk awareness of residents and the operation of a warning system. Historic flood marks are placed along river to make residents aware of the flood risk, for instance in the Ara river near the old sluice gate of Iwabuchi. Another example of a public campaign was in June 2001, when a ‘Flood prevention month’ was organized by the Tokyo Bureau of Sewerage to demonstrate flood prevention activities and explain the role of the sewerage system (TMG, 2005). In addition, hazard maps are made of areas that are susceptible to flooding. These hazards maps are publicly available and distributed among residents to improve their response time in case of an emergency. In 1998 in Kohriyama City in the Fukushima Prefecture an evacuation order was issued because of imminent flooding. The Evacuation ratio of people who had seen the map was 30% against a ratio of 20% for those who had not seen the hazard map. Moreover, their response time was one hour faster. (MLIT, 2002) This example gives an indication that communicating hazards maps to residents has positive effects in Japan. In Japan, there are houses constructed on stilts or on an elevated level to prevent damage in case of flooding. Figure 6.5 shows a house in the Saga lowland plain in the south of Japan. The large difference between road level and floor level will reduce damage during flooding and allows temporary water storage in the urban environment. Paddy fields are often integrated in the urban environment. In addition to contributing to an improved urban environment and making urban areas less dependent on rural areas, these paddy fields are used as stormwater detention facilities in order to control flooding. Also essential infrastructures, for instance metro lines, are protected by removable weirs to prevent the system from flooding. Essential access roads are


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Figure 6.5 Reducing damage in case of flooding: high level difference between road level and floor level. Source: Frans van de Ven

elevated to make evacuation possible during disasters. In every urban district, disaster refuge bases have been constructed that enable emergency services to coordinate the disaster procedures. Roads and bridges to refuge bases have been strengthened and fireproof measures have been taken around these bases (Matsuda, 1990). 6.4.3 Recovery capacity After urban pluvial flooding, it is important to achieve a functioning urban environment again. This includes reconstruction of damaged infrastructure and buildings and restoring ecological, social and economic activities in the flooded area. On a national level recovery capacity is developed by the availability of material and equipment to clean up the urban area and reconstruct damaged buildings. Lock gates have been constructed in the Tokyo urban polders that allow rapid shipments of disaster relief goods. This is important because the accessibility over land can be limited after a disaster. To facilitate quick recovery after a disaster, insurance and disaster funds can be effective measures both of which are risk spreading mechanisms in time. For a premium, the risk is shared with other residents who experience flood risk. In case of disaster funds the risk is spread over multiple years using the tax system. In Japan, there are no disaster funds and residents are responsible for flood insurance themselves. Only a small

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Figure 6.6 Reducing damage in case of flooding: elevated first floor Source: Fransje Hooimeijer

Figure 6.7 Improving recovery capacity by accessibility. Lock along the Arakawa, designed to enable the transport of goods into the central area of Tokyo after a disaster Source: Rutger de Graaf


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part of the population takes flood insurance because of the high premiums and relatively low pay out rates of 10 to 20% (Tatano, 2005) though government agencies do assist in emergency aid and take care of emergency housing. Because key roads are elevated in Tokyo, emergency services are able to enter the disaster area and start with the reconstruction activities and relief for affected residents. In addition, the provision of information to residents as to which areas are safe again and which areas are not, recovery to the condition prior to the disaster is facilitated. The municipality provides this information by maps and internet. 6.4.4 Adaptive capacity Future developments such as climate change, urbanization and societal demands are uncertain. Reducing uncertainty by predicting climate change and climate impacts is done by multiple international organizations such as the Intergovernmental Panel on Climate Change. By reducing uncertainties, research can contribute to increasing adaptive capacity. However, further research is unlikely to succeed in eliminating uncertainties. Decisions considering urban infrastructures with a technical lifespan of decades have to be made at present in urban areas. Therefore, adaptive capacity mostly refers to the ability of society to deal effectively with uncertain future developments. Flexibility and robustness of technical solutions are important properties. One of the key elements of a successful adaptive strategy is experimenting with a variety of technical, institutional and social measures. This provides society with a wide range of possibilities available to anticipate on uncertain future developments. On a national level, basin to basin radar systems are operated by the national government to effectively predict flooding. Good prediction increases the possibility for society to anticipate flooding and counteract the effects by building temporary flood defense or evacuation of vulnerable areas. In addition, water management and spatial planning are integrated and spatial measures such as zoning plans are important. Changes in the spatial structure of a city cannot be easily reverted. Spatial interventions have to allow for flexible choices to be made in the future. Reservations should be made to be able to retain the capacity to adapt to changing physical circumstances in the future, for instance increased rainfall intensity. Land in high risk areas can be reserved for parking, recreation or wildlife. These are functions that allow more flexibility and are less vulnerable to floods than houses or office buildings. In Japan, for this purpose urbanized river basins that are vulnerable to flooding are designated as Urban River Basins under the Urban River Inundation Damage Countermeasure Act (2004). In an Urban River Basin, permission has to be obtained from the authorities for each development of a certain size that prevents stormwater from infiltrating. Compensating measures have to be taken. Examples are: infiltration and storage facilities on the area that is to be developed. At the municipal level, adaptive capacity is strengthened in multiple ways. In Tokyo, the Metropolitan Government decided to start with a wide variety of storage and infiltration facilities in 1982. Tokyo area has good soil condition of Kanto loam which is a volcanic ash of Mount Fuji. It has good permeability, the order of 10-3cm/sec in a saturated hydraulic conductivity. In Tokyo, places such as schoolyards, parks, car parking or vacant lots were used as storage and infiltration facility. Two examples of infiltration facilities are the permeable connection box and permeable trench.

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The permeable connection box is filled with crushed stones to infiltrate rainwater. The permeable trench is an excavated trench filled with crushed stones with a permeable connection box and a connected perforation pipe to guide and infiltrate rainwater. One of the strategies is the ESS (Experimental Sewer System). This system is implemented to build experience with sewer systems that infiltrate and store runoff. From 1983 to 1995 Tokyo Metropolitan Government has built ESS over an area of more that 1,423 ha with 33,294 infiltration pits, 285 km of infiltration trenches and 484,000 m2 of permeable pavement. This has proved to be efficient in reducing both the total volume of runoff as well as the maximum runoff intensity (Fujita, 1997). The effectiveness of the ESS is illustrated with an example from Tokyo. In the catchment area of Shakujii River and Shirako River, rapid urbanization has taken place. As a result, the amount of runoff increased and the discharge capacity of the rivers was no longer sufficient. The application of ESS, resulted in a 60 percent reduction of the peak discharge (Fujita, 1984). Another measure that was implemented in the ESS program is the application of permeable pavements. Such surfaces are an alternative to impermeable concrete or asphalt surfaces which would otherwise produce rapid storm water runoff. Permeable pavements enable water to infiltrate into the ground rather than converting it to runoff. There are different types of permeable pavements. Ordinary tile and brick pavements have significant infiltration capacity (Ven and Voortman, 1985). Permeable

Figure 6.8 Detail of street infiltration box Source: Tokyo Metropolitan Government


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asphalt or concrete can also be applied. The foundation material under the pavement often consists of coarse gravel or sand. In the foundation material, occasionally a subsurface drainage pipe is constructed. Maintenance (street cleaning) to keep the infiltration capacity sufficient is necessary in intensively used areas. Permeable asphalt has a high percentage of voids in which stormwater is infiltrated directly. Unfortunately, it has less strength than ordinary asphalt so the application is limited to sidewalks and small roads with a width of no more than 5 meter (Fujita, 1984). The use of permeable pavements in parking lots is also becoming common in Japan (Fujita, 1997). Porous concrete blocks are mostly used for the construction of permeable road surfaces. Stormwater can infiltrate through the bodies and their joints. They are made of cement and coarse aggregate without sand. The high void ratio makes the infiltration rate similar to permeable asphalt pavement (Fujita, 1994). Special attention is needed on maintenance of the permeable asphalt pavements. They are easily clogged by soil particles and debris. The pavements can be sufficiently cleaned with high pressured water. This method restores the pavement with its original infiltration capacity. However, a drawback is that muddy water flows into the sewer system. Until 1992, the Tokyo Metropolitan Government has already built about 494,000 m2 of permeable pavements which is about 2.3 percent of the total street area (Fujita, 1994). In addition to implementing technical facilities, the ESS program has provided information and experience on issues such as operation and maintenance, effectiveness, monitoring, and involvement of stakeholders. Knowledge about infiltration systems was further developed, which finally led to the publishing of the Engineering Guideline for Rainwater Infiltration Facilities by Association for Rainwater Storage and Infiltration Technology in 1995. As a result, the application of infiltration facilities became more popular. In Koganei city (Population 110,000) in Tokyo 49% of the houses are equipped with soakaways to infiltrate stormwater in the soil (Fujita, 2007). In new town areas measures have been taken to mitigate impacts of urban developments on the natural water cycle and to adapt to the natural water system.

Figure 6.9 Illustration of Experimental Sewer System in Tokyo Source: Shoichi Fujita

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Figure 6.10 Adapting urban development to the natural water cycle in a new town area Source: Jun Matsushita

In addition, digital warning and information systems are becoming more and more advanced like the Sewerage Mapping and Information System (SEMIS) in 1986, the Tokyo Rainfall Radar System for Tokyo Area (1988) and the AMESH Rainfall Radar system (2006). These systems enable effective anticipation of the impacts of flooding, as such it is an adaptive measure. The AMESH system provides real time rainfall data that is used for the operation of sewers and wastewater treatment plants. This information is accessible for residents via the website.

6.5 SECURING WATER SUPPLY: FOUR COMPONENTS TO REDUCE VULNERABILITY The per capita availability of water resources in Japan is low compared to most other countries, see also chapter 1. Moreover, the variability of precipitation over the year is large. Therefore, in Japan all four components to reduce vulnerability for droughts are utilized. 6.5.1 Threshold capacity In Japan a large scale centralized water supply has been developed to secure water supply. Reservoirs have been built to cover seasonal changes in precipitation. For this purpose the national government introduced the Multi-Purpose Dam Construction Act in 1957 to meet increasing demand during the economic reconstruction period. These reservoirs are often multi purpose reservoirs that are also used for hydropower and flood control. In addition the Water Resources Development Promotion Act was issued in 1961 to meet the rapidly increasing water demand. Many multipurpose dams were constructed as a result and comprehensive water resources development plans were made. Large amount of groundwater were also utilized for residential and industrial purposes. Over extraction resulted in drastic land subsidence in Tokyo. Inter basin water transfers are used to increase the capacity to prevent damage during droughts.


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Figure 6.11 Scheme of the Japanese flood forecast system to effectively reduce flood damage Source: Ministry of Land, Infrastructure and Transportation

The amended River Law has now created a new system that enables water users to transfer their water rights to other users. The final decision on these water transfers is made by the river administrators. In Tokyo, water is mainly supplied from rivers and reservoirs. The total amount of water that is secured by the Waterworks Bureau of the Tokyo Metropolitan Government is 6,23 Mm3 per day, this amount is produced by 11 purification plants and distributed by 34 principal water supply stations and 24,782 km of distribution line. A total amount of 12 million people are supplied with water by the Tokyo water bureau. Water leakage rate has successfully been decreased by maintenance and replacement of infrastructure. The total leakage rate decreased from 10.2 in 1992 to 5.4% in 2002 (Motoyama, 2004). The main water sources are the Tone, Ara and Tama rivers. Currently, the Tone river is the main source and supplies 78% of the water supply in Tokyo (Motoyama, 2004). The Tokyo metropolitan area relies heavily on these rivers and the water supply capacity of the rivers is almost at its limit. In the Tama River for example, 80% of the river flow is withdrawn from the river for municipal water supply. Consequently, 75% of the river flow is treated wastewater (Wagner et al., 2002). Also in other rivers in Tokyo, the percentage of effluents in the urban rivers is considerable, with percentages ranging from 17% to even 95.6% (Furumai, 2007). 6.5.2 Coping capacity Rainwater use, stormwater harvesting, greywater recycling and wastewater recycling are technical measures that can assist in reducing impacts of droughts. The Japanese

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Figure 6.12 River water resources in the region fo Tokyo Metropolitan Area, dotted lines show the water transfers between rivers that can be used during droughts Source: Ministry of Land, Infrastructure and Transportation, 2002

national government has actively promoted private initiatives by builder-pay principles. Subsidiary systems to enhance recycling of waste water have been introduced and alternative water use has been mandated for large urban development and urban renewal projects. In addition to the emergency supply system, water use restriction can be issued by the authority to reduce damage in case of droughts. The River Law amendment of 1997 requires users to take measures in case of droughts or expected droughts. Moreover, river administrators are required to provide information about reservoir levels and enact water reduction measures to residents. Measures are also taken at the municipal level to effectively cope with droughts and water supply disruptions during disasters. The Waterworks Bureau of the Tokyo Metropolitan Government has established an emergency water supply system. There are 195 emergency water supply bases within two kilometers of each resident in Tokyo to improve the city’s coping capacity in case of disasters such as droughts. These emergency bases can supply three liters of drinking water to 12 million people during four weeks. The emergency water tanks constantly reserve fresh water from the main distribution network (Waterworks Bureau, 2005). At the same time, the Tokyo Metropolitan Government is increasing coping capacity by demand management. A cumulative rating system is applied in which the water price increases with higher water use. Demand management is further enhanced by promoting water saving behavior and appliances. In 1974, it became obligatory for urban development project of 30,000 m2 or more (recently upgraded to 10,000 m2), to apply water reduction measures such as rainwater use or water recycling. In 2003, a new guideline was established for efficient water utilization and to continuously


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Figure 6.13 Location of emergency water supply bases in the city of Tokyo, on the right side of the map,Tokyo Bay Source: Waterworks Bureau, 2007

improve water efficiency with increasing targets. In addition, water transfers within the Tokyo metropolitan area take place to reduce damage and the impacts of droughts, as figure 6.12 shows. 6.5.3 Recovery capacity During and after droughts, certain sectors have priority over others for water resources on a national level. Inter-sector water use converting is used to recover from droughts and to establish a functioning water system again. Drinking water supply has the highest priority of the water use functions. In Tokyo, the Waterworks Bureau has established an Emergency Water Services Squad to handle unexpected accidents and emergencies in order to recover quickly. The squad consists of six water tank trucks, one anti disaster vehicle, three emergency publicity cars and four investigations cars. This squad is available around the clock to be able to rapidly reestablish a functioning water system after an emergency. Moreover the squads organize emergency preparedness trainings with other government agencies every year (Waterworks Bureau, 2007). Multi source water supply is another measure that is used to more successfully recover from droughts and other emergencies. Tokyo does not rely on only one source, a variety of water sources are used: river water, stormwater, grey water, reclaimed wastewater. As a result the recovery to a sufficient water supply system is quicker if one of these sources is affected. Some municipalities have implemented in house water recycling systems and rainwater utilization systems. A good example is the Tokyo Dome. In the Tokyo Dome water retention capacity has been installed to enable

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Figure 6.14 Treatment scheme of runoff and recycled water in Tokyo Dome Source: Tokyo Metropolitan Government

Figure 6.15 Tokyo Dome Source: Rutger de Graaf


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utilization of rainwater for low quality purposes such as toilet flushing. Stormwater from the roof (16,000 m2) is stored in retention storage of 3000 m3 under the stands. Of the total amount of storage, one third is reserved for firefighting, one third is reserved for toilet flushing and one third is kept empty to use for stormwater retention during heavy rainfall. In normal years hardly any water is used from the main water pressurized water system for toilet flushing. As a result water use is much lower and the building is less vulnerable for droughts. The ability to bounce back after a drought is higher because it has multiple water sources at its disposal. 6.5.4 Adaptive capacity Anticipating uncertainties of future water demand and supply can be undertaken by studies on climate change impacts on water resources and water use projections. In Japan, basin to basin radar systems are installed that can assist in anticipating on droughts. Anticipating future uncertainty with regard to changes of water supply and water demand takes place by integration of water management and spatial planning. By innovative forms of urban design, recharge of runoff to the groundwater is promoted and urbanization is prevented in areas that are important as water catchments. In addition, subsidies, corporate or income tax benefits and low interests loans are available for projects that utilize alternative water resources. There are approximately 2,800 large scale systems of water recycling or rainwater use in Japan. At a municipal level, adaptive capacity to secure water supply can be improved by considering the full range of urban water sources and their possible functions. Examples of urban water sources are river water, groundwater, desalinated sea water, stormwater, grey water and recycled water. By utilization of the full range of urban water resources in a flexible way, i.e. according to the local circumstances, the city is better able to adapt to its physical surroundings. Because society has predominant experience with utilizing treated river water for all residential and industrial purposes, demonstration projects

Figure 6.16 Stormwater utilization scheme in a Japanese house Source: Shoichi Fujita, 2007

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with other modes of water supply are necessary to build experience and reduce uncertainties. Or like the Australian water expert Tony Wong puts it (2007): “Like a shared portfolio, flexible and cost effective access to the diverse water sources will be underpinned by a diversity of centralized and decentralized water infrastructure”. In Tokyo there are many demonstration projects with other modes of water supply and the use of a full range of urban water resources for all kinds of urban purposes. There are many examples with regard to the use of stormwater besides the previously mentioned Tokyo Dome, where stormwater is used in Tokyo for functions such as toilet flushing and firefighting. Residents are encouraged to install stormwater storage on their private property. The subsidy system was established in 1995. There are 850 locations where stormwater is stored (2001), 566 public buildings and 284 private buildings (Furumai, 2007). Figure 6.16 shows a stormwater utilization scheme in a Japanese house. Stormwater is used for garden irrigation, carwash and laundry first and afterwards reused for toilet flushing. Treated wastewater in Tokyo is used for many urban purposes, there are 560 locations in which recycled water is used. These locations are private buildings, public buildings and large scale recycling schemes (Furumai, 2007). In 1979, subsidiary schemes were introduced to promote the use of recycled wastewater system (Matsushita, 2007). Instead of a waste, reclaimed wastewater can be considered as a valuable resource with commercial value that is locally available and is in a constant supply. In Tokyo, 8% of the wastewater is recycled for a variety of purposes (Fujita, 2007). Examples of functions are: road cleaning, sewer cleaning, pavement cooling, train cleaning, urban stream restoration, heating and cooling of buildings, low quality residential purposes, park irrigation, firefighting, and snow melting on public roads. The Ariake wastewater treatment plant in Tokyo

Road cleaning

Park irrigation

Sewer cleaning

Cooling of pavement

Train cleaning

Urban stream restoration

Figure 6.17 Multiple uses of recycled water in the urban environment such as road cleaning, sewer cleaning, park irrigation, cooling of pavement and urban stream restoration Source: Fujita, 2007


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supplies treated effluent to a nearby apartment complex for toilet flushing. The wastewater treatment plant supplies the water at a competing rate compared to normal drinking water supply. In the Shiodome, Tokyo, experiments are executed to use effluent to cool roads in order to contribute to reduce the urban heat island effect. Another innovative approach is the use of effluent for heating and cooling of buildings such as hospitals and hotels. One of the buildings where this concept is applied is the Tokyo Dome Hotel. Recycled wastewater is also used for landscaping, irrigation and urban stream restoration. The Kitazawa is an example of a severely degraded urban stream in Tokyo that uses recycled water for regeneration of the river, this example will be further described in chapter 8. The given examples show that by using multiple urban water sources for a variety of purposes, experience with new modes of water supply is built and the dependence of external river water resources decreases. Therefore, multisource water supply can be considered an adaptive strategy.

6.6 IMPLEMENTING VULNERABILITY REDUCING MEASURES The analysis of the Japanese water supply and stormwater management with the vulnerability framework illustrates the wide range of measures that can be applied. The vulnerability framework can contribute to the development of a more comprehensive water policy. However, the implementation process of these measures is crucial. In the so-called high economic growth period in 1960, Japan had to introduce the basin management systems due to extremely rapid urbanization. During this period, the need for new infrastructure outstripped society’s ability to put it in place these infrastructures, because of weak governance at both national and municipal level. The urban growth control measures were feasible in the UK through the introduction of the green belt to separate densely populated urban areas and less populated suburban areas. In Europe and the US, zoning rules for spatial development were established that were based on public priorities and values. However as chapter 2 indicated, these measures are rather non-applicable in Japan because of strong landownership and the absence of a civic society. Figure 6.18 shows the background and composition of the basin management systems which are needed to mitigate pluvial flooding and solve water shortages. These systems consist of two elements: structural measures and non-structural measures. The non-structural measures are established based on the private initiatives, some of which are legalized by the city planning law to prevent discordant development. They have been workable to offset the gap between the social needs for infrastructure developments and possible deeds by responsible public bodies particularly during the high economic growth period. In addition, they are contributing to promote adaptive measures to make Japan less dependent on structural measures and more sustainable with resources consumptions. 6.6.1 Management of pluvial flooding Japan had to cope with the high economic growth period urbanization-induced flooding during the high economic growth period. Herein, national government had put priority on flood damage prevention in the trunk-rivers based on structural measures

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Figure 6.18 Total Framework for basin management systems Source: Jun Matsushita

such as construction of multi purpose dams and floodways. The multi-purpose dams are mostly cost effective through simultaneous implementation of both flood-control and water resources development including power generation. On the contrary, municipal government had become responsible with little financial resources for the damage reduction against urbanization-induced flooding in tributary small scale rivers in urbanized areas. Herein, private initiatives were introduced for storm water runoff reduction based on the cause-to-pay principle and legalized in the city planning law. On site type storm water retention systems were the main stay for this purpose. Then, stormwater infiltration


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systems became popular upon 20-year verification on the sustainability of these systems. Further, these stormwater runoff-reduction measures are incorporated into the comprehensive flood mitigation systems. For additional damage reaction, Japan established flood relief organizations basinby-basin which are composed of local governments and concerned citizen groups. Quite recently, most local governments decided to disclose flood prone area maps arousing local population consciousness toward flood risk. 6.6.2 Management of water supply Japan is relatively rich in water resources during the monsoon season. However, the country had become less dependent on local water resources due to rapid population increase during the economic high growth period. Tokyo Metropolis faced water shortages during Tokyo Olympics in 1964 and had to introduce basin-to-basin water distribution systems in line with the construction of multi purpose dams. Together with the local municipality water supply capacity had to be expanded to meet the everincreasing demand. In addition, the oil crisis hit Japan around the mid 1970s making people realize the necessity for reducing their dependence on foreign resources. This reminded the Japanese people of the tradition of ‘Mottainai Mind’ or ‘make-the-mostof-resources’ philosophy dating back to Edo era when the country had been closed to outer world and survived on local resources. Most local governments decided to introduce cumulative water rate systems for reducing ever increasing water demands. Tokyo Metropolitan Government (TMG) implemented in-house recycling systems for large scale urban renewal projects with total floor area of 30,000 m2 or more (10,000 m2 or more, recently). In addition, Tokyo Metropolitan Government were trying hard to reduce water leakage finally to attain a miraculous 3% leakage ratio. These measures are totally effective in reducing and stabilizing water consumption. Further, Japan introduced damage reaction measures against unexpected dry conditions. Conversion of water use was urgently applied from agriculture sector to water supply sector during summer season when irrigation water for rice cultivation was not needed.

6.7 COMPARISON WITH THE NETHERLANDS Both Japan and the Netherlands have a developed and managed urban water infrastructure. Threshold capacity, to prevent disasters is well developed in both countries. However, the four component vulnerability framework analysis indicates some remarkable differences between urban water management in Japan and the Netherlands. For pluvial flooding, a remarkable example is the large level difference between floor level and road level that reduces damage during flooding. For water supply a remarkable example is the use of recycled water and the availability of an emergency water supply. This reduces the vulnerability because a city no longer depends on one resource but a whole range of water resources, both local and external resources. In the Netherlands the focus is more on preventing disasters by increasing threshold capacity while the other three components are neglected (De Graaf et al., 2007). Also adaptive capacity is well developed in Japan, technology development and demonstration projects for water supply and stormwater management are applied at a

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Figure 6.19 On-site type storm water runoff reduction Source : Urban Development Corporation

local scale. The experimental sewer systems and the use of recycled wastewater for a variety of purposes are good examples. In the Netherlands, spatial reservations for future water storage capacity seem better developed than in Japan. In Japan, spatial reservations for water storage are problematic. The strong status of landownership remains a huge obstacle. Moreover, space in cities and along rivers is even scarcer than in the Netherlands. Because spatial development is much more private sector driven compared to the government planning


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Figure 6.20 In-house recycling systems Source: Jun Matsushita

Figure 6.21 Change of water consumption in Japan (1950s–2000s), water consumption per capita stabilized around 300 liter per capita per day, leading to an annual water consumption of 16 km3 Source: Jun Matsushita

culture in the Netherlands, incentives have been made to promote stormwater infiltration and water recycling among private sectors. Examples are cause-pay-principles, design manuals, subsidy schemes, binding targets and public awareness campaigns. Involvement of the private sector and the creation of a market by binding legislation have resulted in a large and growing eco industry.

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In Japan, the adaptive capacity of technical infrastructure seems better developed than in the Netherlands. The diversity of well developed technical options that have been described in this chapter, provides the Japanese society with a wide range of options to anticipate on uncertain future developments. As such, one should conclude that the adaptive capacity is high. However, this capacity is not the result of a deliberate government policy to increase adaptive capacity. Japan is highly exposed to natural hazards and the country had to react on huge urbanization and land subsidence. Increasing threshold capacity only, was no longer sufficient to protect the urbanized delta. Therefore, other measures became important, leading to a high diversity of technical infrastructure and thus to a high adaptive capacity. In addition there is a political willingness to experiment and to try different options, as the ESS example demonstrates. In the Netherlands, on the contrary, disasters rarely happen. The last major flood occurred in 1953. In addition, the Dutch tradition to protect the country by increasing threshold capacity has been very strong. Currently, it is recognized by the Dutch government that a more adaptive strategy should be applied in Dutch water management to anticipate on climate change (e.g. Brugge et al., 2005). As a result, national policies have been developed to increase the adaptive capacity of Dutch water management. However, these policy programs have not yet materialized in adaptive technical infrastructure. For the Netherlands, it is therefore useful to learn about technical options in Japanese water management. Climate change will result in more extreme rainfall patterns in the Netherlands. Studying the urban water systems of Japan, where the climate is already extreme at this moment provides insight in what the future Dutch water systems could look like. Japan’s urban water systems, illustrate the possibility to incorporate all four components to reduce vulnerability of urban areas. Diversity, private sector involvement, citizen involvement and initiatives at a local scale to supplement large scale centralized infrastructures are crucial. Japan on the other hand, could learn from the Dutch approach to develop climate change adaptation change policies for the long term and on a high spatial scale.

6.8 CONCLUDING Japan is a country that is frequently exposed to all kinds of natural hazards including flooding and droughts. Consequently, coping, recovery and adaptive capacity are welldeveloped in Japan to adapt to changes in the physical conditions. Based on the vulnerability analysis in this chapter it can be concluded that in Japan all four capacities of the framework are used to reduce vulnerability of urban lowland areas. For urban pluvial flood control, not only improving sewer capacity is applied but also risk communication, stakeholder involvement, emergency plans, wet proofing of buildings and elevated houses and infrastructure. Other coping and recovery mechanisms include increasing capacity measures that reduce the effects of flooding such as stormwater infiltration and retention and securing access to flooded areas by elevated roads and emergency ship locks. With regard to water supply, Tokyo does not only focus on better and more efficient water storage and delivery infrastructure but also on demand management, water recycling, water saving technology and a decentralized more flexible water supply. A range of urban water resources are used, including stormwater and recycled wastewater. In particular recycled waste water is used for a whole range of urban functions, reducing


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drinking water supply and decreasing the dependence of the city on external river water resources. In addition, emergency water supply systems have been installed to better cope with droughts and other disasters that may disturb the water supply system. To better adapt to future water shortages, demonstration projects with new modes of water supply are executed and new technical options are developed for the future. Examples are the Experimental Sewer Systems (ESS) and demonstration projects with multiple urban water sources such as stormwater, recycled water and wastewater effluent. This strategy provides diversity to the options which society has available to face uncertain future developments and disturbances. The Japanese example shows that including all four vulnerability components is a useful guiding principle to develop a more comprehensive strategy to reduce vulnerability of urban lowland areas.

Chapter 7

Development of lowland areas Hiroyuki ARAKI 1 and Olivier HOES 2 1

Institute of Lowland Technology, Saga, Japan Section of Water resources, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands 2

7.1 INTRODUCTION After World War II in Japan many polders have been reclaimed from the sea and lakes. Most of them are used as farmland, but large tracts of land were reclaimed as cheap industrial and residential areas. During the postwar high economic growth period, the population settled increasingly in these low-lying urban areas, which became the heartland of economic activities. Currently more than half the Japanese population is concentrated in low situated areas that are prone to flooding. These areas face typical lowland problems such as land subsidence, salinity and high flood risks. The amount of areas below mean sea level have emerged in Japan because of continuous land subsidence, and draining lakes. In these areas the water level is controlled artificially by installing storage capacity and pumping stations. This causes the soil particles to orient irreversibly to a more compact structure. In this chapter, the building process and management of low land polder areas is described from a civil engineering point of view. The best moment to implement new urban water management concepts is at the moment of polder development. That is the phase in which changes in the concepts of water supply, sanitation, flood protection, pollution control can be applied. Polder development includes the technical and organisational aspects of the urban development process. It includes clearing sites, the main earthwork, installing drainage-systems, stormwater and sewerage disposal systems and the construction of open water, civil engineering constructions and building lanes/paths, together called ‘building site preparation’. Moreover, urban development in the polder has a relation to urban design, making arrangements between the stakeholders, amenities and recreational facilities, installing cables and piping, installing street-lighting, etc. It is the complex process of realizing a new town section or reconstructing. This chapter describes the process of urban/polder development in low-lying areas in relation to the development of urban water system in Japan. Studying low land development in Japanese polders from a Dutch perspective is particularly interesting because some of the Dutch water management approach can be recognized in the polders in Japan. An overview will be given of lowland development in Japan, methods to improve poor soil conditions after reclamation, subsidence, and design methods and criteria.

7.2 RECLAMATION OF LOWLANDS Lowland areas are flat and wet areas in deltas and coastal regions of the world in which human activities take place. Many lowland areas cover a mixture of agriculture,

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Figure 7.1 Japan covers 330,000 km2 and has a 30,000 km coastline Source: Olivier Hoes

industrial and residential areas. For the undeveloped deltaic and coastal areas, a broad variety of terms exist; marshes, swamps, mangroves, wetlands etc. These lower flat areas near the rivers along the coast were preferred centuries ago for the development of settlements. Later on these settlements on the land soil transition became important trade junctions, as of the presence of fertile soil for agriculture, the possibilities for fisheries, and because the rivers were an important means for transportation. Lowland areas can be classified based on the drainage characteristics in: ● ●

Low foothills, which are well drained and never inundated; Pleistocene terraces, which are poorly drained and occasionally inundated for short periods;

Development of lowland areas ●

●

●

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Alluvial plains, which are very poorly drained and inundate regularly for a long time; Marine plains, which are very poorly drained and inundate regularly for a long time; Peat formations, which are permanently inundated, except for some dry periods.

In Japan, the majority of urbanized cities and polders were developed on alluvial plains. Therefore, these cities face various lowland problems as salinity, subsidence and high flood risks. Marine plains along the 30,000 km coast line are valuable for nature conservation and coastal environment. However, the decrease of tidal flats and dry shoals due to land reclamation or the development of coastal areas has become a keen concern in Japan. Peat formations can be found on Hokkaido. Land reclamation had already started in seventh century Japan, around the Ariake Sea for instance, where the altitude was naturally raised due to soil deposition. More artificial reclamation starts around the thirteenth century for the development of paddy fields at various places in Japan. One of the techniques applied is silting up between brushwood dams, comparable with the technique in Europe known as the Sleeswijk-Holstein method. It takes 10–20 years to completely reclaim the land by means of brushwood dams. This type of land reclamation was applied either individually or private investments were used until the eighteenth century. It gradually became public works after the Meiji Era (nineteenth century), as the reclamation projects became larger and were more comprehensive pieces of engineering works. The history of land reclamation is extensive in Japan. Thousands of small reclamation projects may have been carried out along the tremendous long coastline. Only Canada, Indonesia, and Greenland have a longer coastline, but theirs surround a much larger surface. After the World War II, an increase in food production, to become self sufficient, had a high political priority. Some laws relating to reclamation and land development, such as the guideline of urgent reclamation (1945) and the act for comprehensive development of the national land (1950) were enacted. Most Japanese principal larger reclamation projects were a result of these acts such as Kojimawan (Okayama), Hachirogata (Akita), Kahokugata (Ishikawa), Isahayawan (Nagasaki), NakaumiShinjiko (Tottori and Shimane). The initiative was begun by the government, as they had planned to develop in total about 100,000 ha of new farmland. The Japanese government invited Professor P. Ph. Jansen, from Delft University and Ir. A. Volker, chief engineer of the Zuiderzee project, from the Netherlands in order to get advice about large polder projects. Many Japanese reclamation projects were planned with their suggestions on techniques and philosophy. For instance, the Ariake Sea comprehensive development plan was similar with the Zuiderzee project in the Netherlands, which was a multiple land reclamation system (See Table 7.1). At that period, the reclamation of lakes, as well as tidal land reclamation (e.g. coastal marshes and reclamation of shallow seas) was planned. Jansen and Volker inspected many sites in Japan, and compiled the so called Jansen report (Jansen and Volker, Some Remarks on Impoldering in Japan, 1954). This report mentioned that it would be possible to achieve the Ariake Sea comprehensive development plan, even though this project is larger than the Dutch Delta Works. However, the available Japanese techniques and experiences were not enough for such a mega

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Urban water in Japan Table 7.1 Zuiderzee polders in The Netherlands

Source: Olivier Hoes

Figure 7.2 Hachirogata polder (North-West Honshu) Source: Google Earth

project. Thus it was recommended to proceed with the Hachirogata and Nagasaki projects, to gain experience before starting with the Ariake Sea. In time, the Ariake project was reduced to the Isahaya Bay Reclamation project and finally completed in 2007 through twist and turns. The Hachirogata project is one of the biggest reclamation projects in Japan (Figure 7.2). Before reclamation the brackish Hachirogata lake was the second largest lake next to the Biwa lake. The lake was reclaimed as it was very suitable, because of the shallow water depth of four to five meter below mean sea level. The purpose of the project was multiple: – –

To increase food production, To improve flood protection,

Development of lowland areas

– –

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Continuous agriculture by successors, Establishment of a new model of farm villages.

The polder is 17,000 ha large and was reclaimed between 1963 and 1966, taking 20 years to complete the project. The evaluation of the project is divided by both ways of successes and failures, caused by the change in economy and developments in agriculture itself. Nevertheless, the project can be regarded as an important pilot project, from both a technical point of view (very soft clay), but also through the related socio economical issues. While most land reclamation projects for the development of new farmland began between 1940 and 1960, the food problem was gradually improving. So, the government continued the policy by changing parts of the farmland use from paddy fields to vegetables or animal industry. However, the urgency decreased, and only a few projects were planned after the 1970s. Illustrative to this process is the Nakaumi project. The first plans date from 1963, when the Ministry of Agriculture and Fisheries decided to re-develop Nakaumi Lake, which is Japan’s fifth largest lake. However, in time the project plans purpose shifted over the decades: from the need to create additional paddy fields, to build a heavy chemical and industrial area, to grow vegetables, and to develop a new city. Under the pressure of expected environmental problems, the project stopped in 2002, after only 1,689 ha had been reclaimed. Besides through reclamation, urban areas have also been developed by landfill; particularly in mega cities like Tokyo, Nagoya and Osaka where the value of land is high. Old landfill areas, developed since the nineteenth century, were originally intended for paddy fields or harbor extension. Nowadays, these plots are all transformed into urban areas. The more recent landfill projects after WWII were planned straightaway for the expansion of complete urban areas, with all the urban facilities; factories, residential areas, offices, shops, schools, public facilities, railways, stations, roads, airports, parks etc. Some of the landfill projects completed had specific purposes, like airports, or industrial complexes, which need a lot of space, and are difficult to plan on the mainland. Especially, because dispossessing landownership is a difficult process in Japan. Comparable with the shift in purpose of the Nakaumi project, also the future land use of landfill projects under construction transformed in time to changes in the economic climate. Some projects developed for industrial complexes are nowadays used for housing as the developers did not succeed in attracting enterprises. Additionally the current public concern for the environment legitimately limits the development of new reclamation projects. An overview of developed lowland areas is given in Figure 7.3 and Table 7.2.

7.3 SOIL-RIPENING After reclamation the soils at the bottom emerge from under water as soft mud. So, to be able to develop the area, the consistency of the soil has to change from nearly liquid to firm. This can be referred to as ripening of the soil: ●

Physical ripening The soil ripening process starts with the evaporation of excess water from the loosely packed saturated mud. When the groundwater level drops, the volume of

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Figure 7.3 Polders in Japan constructed after WW II Source: Polder of the world, 1982

●

●

the soil reduces irreversibly. This reduction is caused by shrinkage and settlement, and induces cracks and subsidence; Biological ripening The biological ripening of the soil involves the development of aerobic microbiological life within the soil. Especially, the development of sufficient nitrification capacity can take considerable time. After drying the soil, the available organic matter tends to be quickly consumed, which makes it necessary to add sufficient organic fertilizer; Chemical ripening Marine soils are salty and rich in sulphides. The salt has to be leached from the soils, before they can be used to grow crops. The oxidation of the sulphides may lead to the formation of acidic soils with pH values as low as 3–4. Drying deeper


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Table 7.2 Polders in Japan constructed after WW II

Source: Polders of the World, 1982

is important to oxidize sulphides to sulphates which can be easily washed out via the drainage system with salt. Additionally, lime is used for de-acidification with organic fertilizer which helps buffer capacity of soil. Phosphorus is also always lackin in the early stage because of combining iron-sulphate. The ripening of mud soil normally starts at the surface, initiated by evaporative drying, from where it slowly extends to deeper soil layers. The rate of extension decreases as the ripening reaches deeper into the soil and as the ripening of the soil progresses. Full ripening may take centuries. Ripening does not extend below the deepest fall of the water table as reached in a dry period. The soil volume reduction reveals itself in the field by subsidence of the soil surface and the formation of cracks. In time these cracks are filled up from the flanks and/or from the surface and in the long term all ripening shrinkage and settlements translates itself into subsidence. The shrinkage and settlement of unripened soil upon drying is irreversible. Only small parts of the original volume can be regained by swelling when the soils are rewetted. To stimulate physical ripening different techniques exist. In Japan, perforated conduit pipes are mainly used to accelerate drainage and drying of soil during the first years after reclamation. Main pipes are installed around 0.8 m–1.2 m below land surface every 10 m. Additionally for enhancement of drainage, sub conduit pipes are buried around 0.5 m depth in a direction perpendicular to the main pipes every 10 m. Sometimes, this sub conduit is covered by chaff to increase permeability. The main

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Figure 7.4 Vertical ripening cracks below 0.5 and 1.0 m below surface level Source: Groen, 1997

pipes are opened to drainage ditches and finally the drained water is pumped up to the sea. In the early phase after reclamation these drain systems work for soil ripening. Subsequently these pipes are used for drainage from paddy field for two-crop system. The most recent reclamation projects in the Netherlands were the Zuiderzee polders (see Table 7.1). The size of these polders would have made it a harsh job to bury drainage pipes for the ripening process on a small interval (see Figure 7.5). So, to stimulate the ripening process reed was spread with airplanes and helicopters over the areas. Reed is a very good crop for the first year, as it can take root easily, grows in saturated soils, and has a large transpiration coefficient. Only after the soil is able to support some equipment, ditches are dug. After reed, the second year crop is coleseed, and subsequently wheat (third year), barley (fourth year), and oats (fifth year) are sown.

7.4 LAND SUBSIDENCE The withdrawal of (ground) water will result in a gradual lowering of the ground surface elevation. This lowering is called land subsidence and caused by consolidation of sediments and sometimes by oxidation of organic deposits. Soil consists of solids, air, and water. The pressure transmitted through the individual solids is called the intergranular pressure. So, if we lower the water level, we


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Figure 7.5 Lake bottom in The Netherlands just after reclamation Source: Nieuwland Erfgoedcentrum

increase the intergranular pressure, which will move the individual solids in time to each other. The intergranular pressure can be calculated as the difference between the total ground pressure and the hydraulic pressure at that depth: σp σt σh in which: σp intergranular pressure [kN/m2] σt total ground pressure [kN/m2] σh water pressure [kN/m2] How the intergranular pressure increases is demonstrated with an example: Assume a lake with a water depth of 4 meter (γw 10 kN/m3), with a soft clay layer on the bottom 6 meter thick (γs 15 kN/m3). This clay layer is on top of a non subsiding dense layer: The water pressure at the bottom of the clay layer is: σh γw h10 10 10 100 kN/m2

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Figure 7.6 The intergranular pressure increases by reclamation Source: Olivier Hoes

The total pressure equals: σt γw h4 γs h6 10 4 15 6 130 kN/m2 Hence the intergranular pressure is: σp σt σh 130 100 30 kN/m2 Reclaiming this lake, will reduce the waterlevel to decrease to approximately 5.5 below MSL, which is 1.5 meter to below the top of the clay layer. As the soil is still saturated the total pressure will not change, and thus the intergranular pressure will increase: The water pressure at the bottom of the clay layer is: σh γw h6 10 4.5 45 kN/m2 The total pressure is still: σt γs h6 15 6 90 kN/m2 Hence the intergranular pressure is now: σp σt σh 90 45 45 kN/m2 This increase in intergranular pressure, must result in a decrease of the void ratio, and a compression of the soil layer, and consequently subsidence. The final settlement can be estimated according to the formula developed in 1925 by Terzaghi: ∆z

D σp, av ∆σp, av ln σp C

Where: ∆z subsidence [m] σp,av average particle pressure before the drop of the water table [kN/m2] ∆σp,av increase in average particle pressure due to the drop of the water table [kN/m2] D thickness of the soil layer [m] c consolidation coefficient [-]


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Typical values for the consolidation coefficient of clay soils are between five (unripened) to 20 (ripened). With the values from the example:

∆z

D σp ∆σp 1.5  11.25  4.5  33.75    0.9m ln ln  ln   3.75   18.75  c σp 5 5

Terzaghi’s theory is based under the assumptions that: – – –

The soil is homogenous and completely saturated with water, The particles and water are incompressible, The hydraulic conductivity is constant during consolidation.

Furthermore, the final subsidence depends on the estimation of the initial void ratio, final bulk density, and the assumption that the groundwater at all times corresponds to the prevailing hydrostatic pressures. Though in clay soils excess soil water pressures may continue to exist for a considerable time after reclamation. So, the result accuracy from this formula is limited. Subsidence affects the planning of the drainage system of the reclaimed area. Usually medium (10 to 25 years) and long term (100 years) subsidence predictions are made for those engineering works with technical or economic time horizon of the same order of magnitude. Next to reclamation, subsidence also occurs if groundwater is extracted for drinking water or industrial purposes. Since 1910 many deep wells were drilled, as a consequence of the development of modern drilling machines that pumped out water excessively from the wells. Land subsidence was first identified in Tokyo’s Koto Ward in the 1910s and in Osaka in the 1920s. Maximum subsidence was observed in the Tokyo lowland in the Kanto Plain of 63 cm between 1923 and 1926 and 56 cm between 1926 and 1930 (Imamura, 1932; Tohno, 1994). Also during the 1930s, subsidence rates of more than 10 cm/year were observed in Tokyo and Osaka areas. During World War II subsidence rates were small due to a large reduction in the withdrawal of groundwater from wells. The rapid industrial development around 1950 caused an increase in subsidence similar to the pre-war situation. In the Osaka lowland the groundwater level dropped by about two meters a year between 1949 and 1960. Since 1955 subsidence is recognized as a nationwide problem, not only in Tokyo and Osaka but also in adjacent and other areas including the Niigata and the Saga plains. Two laws have been enacted and enforced to reduce the yields of groundwater; the ‘Industrial Water Law’ in 1956 and the ‘Law Concerning the Regulation of Pumpingup of Underground Water for Use in Buildings’ in 1962. In addition to these laws, local governments formulated ordinances to control the pumping up of groundwater, to develop and use surface water as a substitute for groundwater, and to raise awareness of the prevention of ground subsidence. However it took up until around 1980 before the result of various counter measures and regulations slowed down the subsidence rate considerably. At present maximum measured subsidence in Japan is about three to five cm/year in Uekusa, Sanbumachi (Chiba Prefecture), Kanto Plain in Koshigaya City (Saitama Prefecture) and in Yokohama City (Kanagawa Prefecture) (Tohno, 1994).

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Figure 7.7 Change of groundwater potential in Tokyo Source: Ministry of the Environment Government of Japan

Another effective act that restricts the amount of groundwater withdrawal to prevent land subsidence is the ‘Guideline of measures for preventing ground subsidence’ One of the consequences faced due to rising groundwater level is that leakage water is now entering the subway tunnels. These tunnels were constructed at the time when the phreatic head was low, and a possible rise was not considered.

7.5 SOILS AND DRAINAGE 7.5.1 Lowland soils Soils of lower deltaic plains can be categorized as: 1. 2. 3. 4.

Coastal saline clays; Fresh clays; Organic soils; Acidic clays.

The thickness of soft tidal clays e.g. in Ariake bay (Kyushu), is regularly between 10 to 40 m while the water content ranges from 50% to 200%. The high water content makes the soil samples very lose, without strength. So the samples cannot be tested without a confining stress. The sensitivity of these soils is very high and influenced by the salt content. Fresh clay deposits in flood plains of rivers change from coarse grained deposits to fine grained as the river approaches the sea. Silt, silty clay and clay layers are found in


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Figure 7.8 History of ground subsidence in typical areas Source: Ministry of the Environment Government of Japan

the lower reaches of rivers. However, fine sandy layers might be inserted between flood plain deposits. These deposits are subject to wetting, drying, swelling, shrinkage, scouring etc. Therefore flood plain deposits along rivers are much stiffer and stronger than those in deltas and tidal flats. Organic soils are formed when the saline or brackish lagoons turn into shallow fresh water lakes. These lakes fill up gradually with organic matter produced by vegetation, which subsequently transform into peat deposits. Peat soils can be found e.g. around Ochiishi (Hokkaido). Sediments from swamps which are organic and contain brackish water develop into acid sulphate soils. The bacteria which obtain their energy from oxidation of organic matter, reduce the sulphatesin turning the water into sulphates and sulfuric acid as a result of aeration or by leaching. The pH values are lowered to less than 4.5. The clay minerals are broken down in these acidic conditions. These soils may become toxic to plants and also concrete structures cannot withstand the high sulphate concentration and need special protective measures. Acid sulphate soil can be found in limited zones in the region of Lake Nakaumi and Lake Shinji (Honshu). 7.5.2 Rural and urban drainage The Ministry of Agriculture, Forestry and Fisheries (MAFF) is in charge of flood control and drainage in agricultural areas. The design concept is based on healthy rice

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Table 7.3 Design precipitation with a 1/10 year return period

Source: Olivier Hoes

cropping, which makes the period of submersion compulsorily less than 2 days. This causes design discharges of 50 mm/hour (see Table 7.3). Rice is one of the principle food crops of Japan. It is different from other crops in that it has a well developed internal conduit system for aerating the roots from parts growing above the ground, this facility allows rice to grow well under anaerobic waterlogged conditions. Paddy is therefore usually the crop of choice for humid semi-tropic lowland plains where waterlogging conditions (high (ground) water levels and surface ponding) prevail naturally during much of the wet season, or may be readily created by the retention of rain within bunded fields and/or by supplying some additional irrigation water. In the past, Japan has implemented large scale programs, aiming at arriving at standard 3,000 m2 fields (30*100 m) with irrigation, drainage and road facilities running along the short ends. Before, field drainage in rural paddy field areas in Japan consisted mainly of small ditches. Ditches were preferred as: ● ● ●

The land requires both surface and subsurface drainage, Farm operations were mostly done manually, The standard of drainage required was not high in paddy fields.

Although nowadays, about 20–25% of the paddy land in Japan has buried pipe drainage, almost all being installed within the framework of government subsidized land consolidation, and crop diversification programs. The advantages of pipe drainage are better trouble free functioning, less cost, less land loss and do not hinder farm operations. The internal drainage conduit systems, applied at the time of reclamation, were developed only for the purpose of two crops (rice and wheat) in the same paddy field. Rice in the summer (rainy season) and wheat in the winter season (dry season). The drainage conduits are closed in the summer to keep the water in the field for rice, and opened in the winter to drain the excess water for wheat which prefers dry conditions. Optimal water depths for modern paddy farming are generally assumed to be in the order of 5–10 cm. The water layer establishes the desired waterlogged growth conditions, but also helps in weed control. Modern short stem high yielding varieties demand strict water depth control as these are more sensitive to a varying and several days lasting excess depth. Yield reductions due to excess depth remain quite limited provided the paddy is not fully submerged for more than two days.


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Submergence by muddy water is more harmful than by clear water as the mud may block the stomata and impose constraints on respiration and photo syntheses. The design rainfall is taken for most situations at critical rainfall duration of 2–3 days and with a frequency of 30 years. Typical Japanese design discharge are 10–15 l/s/ha. Furthermore, when the communities are located at relatively higher places, the capacity of pumps is often designed in accordance with the acceptable inundation level and the inundation duration rather than the peak drainage, which makes the necessary capacity to be usually 1/2 to 1/4 of the peak discharge. In the Netherlands pipe drainage is designed at 0.8 l/s/ha and for water courses and ditches at 1.5 l/s/ha. For crops other than rice, the basic design criteria is to control the water table in the soil in order to create favorable soil water conditions for crop growth and farm operations. Depending on the location soil salinity control may add some requirements. A number of objectives that can be distinguished: ● ● ● ● ●

Improvement of the root zone aeration, Early soil workability after rain, Early warming up of the soil in spring, Prevention of soil structural deterioration, Supporting useful microbiological, and biochemical processes.

Although in most catchments, the urban areas are quite small compared to the rural areas, urban drainage often has a disproportional impact on its hydrological regime. The impact of urban drainage is generally most pronounced quantitatively on the high stream flows. During the rainy season, the water quality is rather good as the precipitation dilutes and flushes any waste water. The water quality deteriorates at low stream flows, and can cause serious environmental problems. Moreover, in lowland areas the velocity of water is generally low due to gradients in water courses and therefore water tends to be stagnant. In case of shortage of river water, the water quality becomes worse due to eutrophication. Nowadays some lowland areas are trying to introduce water conservation. By conserving water in the rainy season, they try to create a higher base flow in the dry season, which keeps rivers environmentally sound. Due to the high percentage of paved areas with low infiltration capacities, and limited retention facilities, stream flow hydrographs of urban areas are much more peaked than those for rural areas. In small highly urbanized catchments, the peak flows at the outlet may be easily three to four times higher than for comparable rural catchments. In contrast to the Netherlands many canals in Japan were lined in the past by bricks or concrete, which allows a higher water velocity. The advantages are multiple: ● ● ●

In order to protect canal bottoms and walls against erosion by flowing water, To increase the discharge by reducing the friction, To limit the necessary space; as there is not enough room in urban areas and steep slopes are required.

At the present time concrete bricks are understood not to be suitable for a healthy aquatic ecosystem. Therefore renovation works are done in some rivers to re-develop

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the function of rivers in order to create a healthier ecosystem, by applying porous/ ecological concrete bricks or creating vegetated unlined canals.

7.6 CONCLUDING REMARKS The basic principles of lowland reclamation, development and flood control in the modern history of Japan and the Netherlands is similar. Dutch knowledge, obtained through the Zuiderzee projects around 1930, were transferred in the impoldering projects constructed between 1950s and 1960s in Japan. Although this was effective in both countries for solving serious flood problems and economical improvements, currently new steps are needed for lowland development and flood control, due to accumulated economic assets and an increasing attention to ecological and qualitative aspects. Moreover, land reclamation might have been indispensable for food production and/or flood control after World War II. The recent socio-economic situation is rapidly changing and there are various ways of flood control. The multiple impoldering method is not always the best way, but the traditional slow reclamation system by depositing silt at tidal lowlands may still be applicable, for example in the Ariake Sea. In contrast to the Japanese lowland areas; 70% of the country is mountainous where both forest management and high water control have the highest priority. In the modern state, after Meiji Restoration, the vertical administrative structure has spontaneously been established for the rapid improvement of mainly the social infrastructure in the lower areas. At the moment this structure of flood management control by river division, urban drainage by sewage division and disaster prevention/drainage in farmland by agriculture division continues. However, this system has often obstructed overall water policies. The integration of policy on flood control or water/land management must become important from now on in Japan.

Chapter 8

Parallel planning approach for urban water management Govert D. GELDOF 1 and Shoichi FUJITA 2 1 2

Geldof c .s. Bathmen, The Netherlands Urban Water Management, Nagaoka University of Technology, Japan

8.1 INTRODUCTION New methods of planning approaches are being developed both in Japan and the Netherlands. Compared to the past different players/factors become increasingly important in the field for example: in Japan the communities have become more influential on the urban development of their area. In contradiction to the Japanese tradition of central government determining everything, the communities have more opportunity to decide with the local government about the qualities and future of their neighbourhoods. To illustrate this change, the Kitazawa River in Tokyo that has been changed to an underground combined sewer because of pollution. The neighbourhood wanted to have the river in sight again because of spatial qualities so the upper part of the sewer has been changed into a nice stream with a pedestrian path in a park like environment with clean water flow from a waste water treatment plant. It is a very successful example of participation of residents in urban water planning. The inhabitants have become designers and water managers rather than consumers only. In this chapter Dutch and Japanese experiences with parallel planning and dealing with complexity in urban water management are presented. The Dutch governments used to apply a serial approach, where in Japan a parallel approach was more common. By combining the Japanese parallel approach and the Dutch serial approach, the planning method of Interactive Implementation emerged. A parallel approach is needed in complex processes, with many actors and uncertainties.

8.2 SERIAL AND PARALLEL Organisations are often locked-in into a working method that is never questioned in a critical way. It is more or less taken for granted that it has to be done the way it has always been done and it’s drawbacks are accepted. In the Netherlands and other western countries a serial approach in planning processes has been applied for ages. This means that in the process several activities are distinguished. These activities are prioritised and executed step by step. When step one is finished, step two starts. In Japan however, the activities are executed parallel. All activities are important, so prioritisation is not really necessary. When possible, it has to be done. In this chapter the implementation of modern stormwater management is investigated. Where in the Netherlands many people studied for years to reduce all uncertainties in

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Figure 8.1 Standard phasing of a project (serial approach) Source: Govert Geldof

the projects and to wait for laws to justify the new techniques, in Japan many ideas were already implemented in a process of ‘learning by doing’. First the serial approach will be discussed in more detail. Then it will be described how stormwater techniques were introduced in Japan. This chapter ends with a short introduction of Interactive Implementation, a working method for coping with complex processes, combining the advantages of the Japanese and western approaches. Case studies of Nijmegen and Kitazawa River in Tokyo are used as illustrations.

8.3 THE SERIAL APPROACH Figure 8.1 shows the heart of the serial planning approach (Geldof, 2005). In many processes in the western world the sequential steps of policy making, planning, design, implementation and maintenance are taken for granted. At each step different networks of people act and each step results in a document or a construction. For relatively simple projects this approach works very well; however, when complexity increases it makes it hard to realise plans. Many plans are never implemented and an important explanation for that can be found in the fact that many professionals rigidly maintain the consecutiveness of activities within a process. In the serial approach, policies are formulated at the national or European government level. These policies are laid down in memoranda or in directives. These formulated policies are the starting point for planning processes and goals. The goals describe the desired values. Packages of measures are composed in the planning process that is aimed at matching the observed state to the desired state efficiently and effectively. These measures are prioritised. Upon decision-making, designs are drawn up and measures carried out. The results of the measures are given in the hands of the maintainers, who make sure that the state of the improved system is maintained, in equilibrium. This serial approach is a strong concept for processes that are linear, predictable and not too dependent on the context. The approach will fail in complex projects, because the complexity is overlooked. Involved parties are taken by surprise by the non-linear dynamics and become discouraged. The practice is wilful and good intentions evaporate. It is clear that the actors involved in the activities of the above described chain of activities are different. The people who draw up policies are different from the people who make plans. The people who make plans are usually not the same people who are responsible for the design, implementation and management. After each activity in the chain, a new group of people takes over the baton. A lot goes wrong here. People who draw up policies give their ideas to the work field when their memorandum has been laid down. They often fear (and rightly so) that their ideas will not be understood correctly in the field. They are not able to completely control the effects. It

Parallel planning approach for urban water management

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often happens that they set up a subsidy scheme to stimulate desired developments. This way, they can also tighten their hold on the process by setting conditions for the subsidy. The result is often that these subsidies restrict the process, which sooner inhibits developments rather than stimulates them. Permits also often have a similar effect. Planners have the impossible task to compose packages of desired measures that cater for all uncertainties that may occur in practice. Certainties are being aimed for because when a planner completes a plan, others will take it from there. The result is that many supporting studies are carried out – mostly model studies – to be certain that the chosen solutions are indeed the best ones. This is why the planning process takes so long. People involved become impatient and suspicious. Despite the interaction in the planning process, residents and companies feel that matters are being decided in back rooms. Support will then erode. In the engineering world, it is usually the case that the people who draw up the designs are different people than the planners. The result is that many subtleties from the planning phase are not translated into the design. This only becomes visible when implementation has started. The remark “this is not what we intended” is a common one from people who were interactively involved in the planning. Designers often draw up specifications without much time for reflection. They only have limited access to the abstract world of policy and planning. They are focused on the tender. They translate from abstract to concrete, but the significance of things is often beyond them. The designs are used to apply for subsidies and permits. When these have been granted, nearly all elbowroom has been taken away for the rest of the chain. This makes it really hard for the people in implementation to be creative. They have to stick to the rules and the rules are getting stricter. A supervisor may discover during implementation that certain things were forgotten during the planning phase and the design phase. It can also become clear that matters could have been designed smarter or cheaper or that changing circumstances have rendered a certain construction redundant. In spite of this, the design is carried out as earlier agreed, because otherwise the subsidies are lost or the permit retracted. This is frustrating to people involved in the execution, especially when they are creative and like to think along. They are the ones who are faced with the complaints of residents who can see that matters are being handled illogically. They are the ones visible out there on the field, while the people at the start of the chain can hide in their offices. Finally, the maintainer of the public space will be handed over the job upon it’s completion. Often it turns out that the planning phase and the design phase have not adequately taken the maintenance aspects into account. Many objects are difficult to manage. Plus, cutbacks in the design often result in higher costs of maintenance. But the budget for maintenance has not been adapted to any cutbacks in the design. The result is that maintenance can only be carried out at a lesser level of quality than desirable.

8.4 A PARALLEL APPROACH In the western world the use of the serial approach is based in the culture. The axiom is that processes need to be controlled and uncertainties have to be reduced as much as possible before you can do something. The objective is to strive for order. The Japanese approach differs significantly. In eastern philosophy it is not the aim to strive for order, but to find the middle way between order and chaos. Too much chaos results in many mistakes; however, too much order results in stagnant behaviour. You have to

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find the middle way between too much and too less. In Japanese that is called “Chu You”. So processes are focusing on bringing them alive instead of controlling them. With that, a parallel approach emerges. Instead of forming the serial chain of activities with packages of prioritised measures, activities that are necessary are formulated and carried out in parallel. That gives the opportunity of having a lot of interaction. When there is too much chaos, new regulations are applied. When there is too much order (stagnant behaviour), stimulating activities are formulated. Ideas are implemented by the principle of ‘learning by doing’.

8.5 STORMWATER INFILTRATION This chapter describes the implementation of new ideas in Japan with the example of stormwater infiltration (see Geldof, Jacobsen and Fujita, 1994), a technique that is implemented in Japan successfully. In the case of a highly urbanised river basin, the systematic storage and infiltration of stormwater is getting popular throughout Japan as an alternative to river improvement work to increase the capacity of a river. Here, stormwater infiltration facilities are installed not only for public areas but also for private housing areas. The ESS (Experimental Sewer System) incorporating infiltration and storage systems in the sewerage network has proved highly effective in dealing with stormwater runoff. Some professionals in Japan realised that it is not always appropriate to discharge stormwater through sewers. Stormwater is not the same as waste water and can be regarded as a source; something that is also a part of Japanese culture. Rainwater is connected to life and to the health of people, so it should be seen as something valuable. However, from a technical point of view it is not simple to change the handling of stormwater, because like in Europe there are many combined sewers in Japan and space is limited. In principle there were five concerns connected to stormwater infiltration (Fujita, 1997): (1) Unknown positive effects Quantitative evaluation of the positive effects of stormwater infiltration was once considered very difficult in Japan due to the extremely complex soil conditions. (2) Maintenance It is expected that stormwater infiltration facilities are hard to maintain. Especial clogging can be a problem. There are two ways to cope with clogging: prevention and restoration. The first priority to prevent clogging is the adoption of a structure with a sedimentation area with a device to shut off the inflow of sediment. (3) Lack of public support Infiltration facilities have to be installed over an entire area, including private land with good cooperation of the local residents. When people do not cooperate, the idea of stormwater infiltration will fail. (4) Possible technical disadvantages Stormwater infiltration is an attempt to artificially augment the natural infiltration process which is impaired in urban areas. In other words, it is an attempt by people to


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imitate natural processes. Because the ability of people is far inferior to that of nature, it is possible that problems may arise. It is impossible to completely forecast at present what those problems might be, but we must be cautious and careful in looking out for reactions to our new efforts. Road management agencies are concerned that the installation of infiltration inlets and trenches on either side of a road may have adverse effects on the road structure, such as ground subsidence. (5) Groundwater contamination Rainwater can be polluted by air pollution and during its discharge process. The former is closely related to wide-ranging global environmental problems while the latter can be solved by placing specific restrictions on the outflow route. It is often said that the stormwater from a house roof is relatively less polluted. However, it has been reported that heavy metals are found in such stormwater if the roof is made of metal. Careful attention should therefore be paid to any stormwater from roofs. The infiltration of water from road surfaces is usually undesirable as the water collects pollutants from the road surface.

8.7 THE IMPLEMENTATION OF STORMWATER INFILTRATION When urban hydrologists started to implement stormwater infiltration, they were aware of the five above-mentioned concerns. The parallel strategy implies that they started to implement the new techniques in several lots to learn from it and to improve the implementation of newer projects. To find answers to the concerns, eleven activities were formulated and handled parallel (Fujita, 1997). (1) Subsidy system Japan has no national laws making stormwater infiltration compulsory. As a result, people are not obliged to install infiltration facilities. To stimulate, the central government introduced a subsidy for the construction of stormwater infiltration facilities. Using this subsidy, local governments can install stormwater facilities in public space and can also offer the subsidy to residents who install these facilities on private property. In the absence of legal regulation, subsidies are an effective means for motivating people to install infiltration facilities on private land. (2) Administrative guidance It is possible for a local authority to compel a local resident or company to construct infiltration facilities even if there are no specific regulations. Any construction of housing or preparation of residential ground over a certain size, whether by individuals or by developers, must be reported to the head of the local authority. In Japan, ‘reporting’ in reality means ‘obtaining a permit.’ Once this report is submitted, it is examined by the local authority in the light of the various local rules. At this point, the developer may be required to install infiltration facilities. Even though such requirements have no legal force, most developers believe that it is generally unwise to ignore an official request. In many cases, therefore, new houses and housing developments are fitted

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with infiltration facilities, by the request of the authorities. Naturally, there are many others who do not install them. (3) Improvement of administrative system Stormwater infiltration was begun about 25 years ago, but neither national nor local governments have set up administrative or fiscal systems for implementing it. Planning, design and construction of infiltration facilities were carried out by a wide range of departments – rivers, sewerage, environment, housing, urban planning, roads, parks, public buildings, etc. – and there was no standardisation, not even within the same local authority. Now this has been changed. (4) Interest of Politicians By doing real projects and showing good results more politicians are becoming concerned about the global and regional environment. Many of them call for promotion of stormwater infiltration in national and local assemblies, during elections, etc. It often happens that they call on administrative bodies to promote infiltration, thus stimulating the administration to act. (5) Including stormwater infiltration in urban planning The Japanese Urban Planning Law requires local authorities to set up urban planning with facilities to be constructed in order to improve the local living environment. The facilities included in urban planning are roads, parks, sewers, etc. In order to achieve an overall effect, comprehensive planning of infiltration facilities also has to be included in urban planning. (6) Standardization of infiltration facilities It is obviously highly inefficient that those who plan and design infiltration facilities have to consider the form, shape, dimensions and structure of the facilities individually. Therefore, technical manuals for design, construction and maintenance have been made to promote stormwater infiltration throughout the country, based on the rich experience in the many plots where the techniques have been implemented and tested. In 1994 the Ministry of Construction started to lay down design standards for soakaways and infiltration trenches on residential land and roads. (7) Public relations activities In order to gain public support, the authorities have provided a variety of information by means of municipal public relations activities. These include advertising, pamphlets, newsletters, videos, symbol marks, character design, display of actual soakaways, etc. There has been an active cooperation with the media like newspapers, television, radio and magazines. Another effective technique is to prepare maps showing areas suitable for infiltration and targeting residents of these areas asking for their cooperation. Local officials sometimes visit each household distributing pamphlets explaining the significance of stormwater infiltration. Other authorities hold public meetings, demonstrations and events to stimulate interest among the public. It is also important for local authorities to systematically request the cooperation of architectural design companies and plumbers who will design and install soakaways and infiltration trenches on residential land.


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(8) International dissemination of information Advertising the fact that stormwater infiltration is a worldwide trend is a persuasive technique for promoting infiltration in Japan. By bringing in Japanese experiences into international conferences and by learning from the experiences in other countries, the quality of the applied techniques has improved significantly. (9) Construction of model district Infiltration facilities are mostly underground not visible to people. That is why a model district has been constructed in Tokyo where the functioning of stormwater is made visible and the mechanisms are explained to visitors. (10) Fostering of infiltration products by companies Anyone making a profit out of infiltration will be enthusiastic about it and will promote it. It is important to set up official standards and guarantees for infiltrationrelated products such as concrete blocks for soakaways, perforated pipes, porous pavements, as well as buckets, baskets, screens, parachutes and so on. (11) Harmony with rainwater utilisation The movement to conserve rainwater as a water resource is gathering momentum in Japan. The first step in the utilisation of rainwater is the use of water stored for flood control. If rainfall exceeds the capacity of rainwater storage tanks in private or public facilities, the excess rainwater will overflow. Then, it will be easy to request diverting the surplus rainwater onto infiltration facilities. Installation of rainwater tanks and infiltration facilities as a set will be a useful means of promoting stormwater infiltration.

8.8 INTERACTIVE IMPLEMENTATION The example of stormwater infiltration shows that the main focus in the process is the implementation. By implementing the stormwater facilities, there is a lot of interaction with different people. In a process of ‘learning by doing’ many people become enthusiastic, like citizens, companies and politicians. In the Netherlands we also have a lot of interaction with many people, but mainly in the phase of making plans. The result is a plan with a lot of support. But support for a plan is not the same as support for the implementation of a plan. The Kitazawa is an example of a severely degraded urban stream in Tokyo that uses recycled water for regeneration of the river. Urban development in the postwar period resulted in a severe decrease in groundwater infiltration. As a result the discharge in Kitazawa almost became zero in the 1960’s. The only water that was still there was heavily polluted wastewater from households. The local authorities decided to cover the river with concrete and make in into an underground culvert. Recently, an urban stream that is supplied with treated recycled wastewater has been created on top of the culvert after requests from residents. Recycled water is supplied from a treatment plant 11 kilometers away by pipe. A double deck urban stream has been created that contributes to increased living quality of the urban environment. The urban stream was designed by the residents themselves.

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Figure 8.2 Kitazawa Double-Deck river Source: Shoichi Fujita

Figure 8.3 Kitazawa river Source: Frans van de Ven

A good mix of Japanese and Dutch traditions can be found in the planning approach of Interactive Implementation (Geldof, 2005), a parallel approach inspired by the Japanese way of working (see Figure 8.2.) It has been applied for the first time in the process of making and implementing a water plan for the Municipality of Nijmegen in the Netherlands (1997 – now).


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Figure 8.4 The principle of working parallel in Interactive Implementation.The activities are on the vertical axis; time on the horizontal axis Source: Govert Geldof

Figure 8.5 Nijmegen Stikke Hezelstraat Source: Govert Geldof

First, a vision is drawn up. This is necessary, because the direction of the development must be known. In drawing up the vision, actors are involved that have a formal task and responsibility in water management. Extensive interaction during the forming of the vision is not required. With the process of the Nijmegen water plan the vision was drawn up in one day, on 11 June 1997, after some preparation. The vision makes people enthusiastic, provides the desired direction and offers enough elbow room for other actors to bring in their own ideas. After drawing up the vision, planning, design, implementation and maintenance run parallel. Many meetings take place between the people who are involved in the different activities. They are going through a mutual learning process; learning from each other. The ‘interactive’ notion mainly pertains to the interaction between planners, designers, implementers and maintainers. The motto of

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Interactive Implementation therefore is: “Not after one another, but beside one another.” Residents, companies and actors from civil society are involved in the process on many occasions. Not just in the planning phase. There is a great deal of interaction with residents and companies in projects at the smaller scale level in particular. With Interactive Implementation many disadvantages of the serial approach are solved. It is not a full copy of the Japanese system, because there are still some cultural differences that ask for other ways of organising a process. However, it has become clear that when new ideas have to be implemented that are complex by nature and show many uncertainties, a parallel approach offers better results. In simpler processes, a serial approach might suffice. It also shows that it is worthwhile to see what is happening in other countries to learn from each other. Eastern and western cultures have different philosophical roots, both with rich traditions. When you are able to combine these and use the best from both, our policies to improve quality of life on this planet can be more successful.

Chapter 9

Challenges for delta areas in coping with urban floods Chris ZEVENBERGEN 1 and Srikantha HERATH 2 1

Department of Urban Water and Sanitation, Core Sustainable Urban Infrastructure Systems, UNESCO-IHE, Delft, The Netherlands 2 Environment and Sustainable Development Programme, United Nations University, Tokyo, Japan

9.1 INTRODUCTION In Asia and Europe floods are the most common natural disaster and in terms of economic damage, the most costly ones (Cred, 2008). Although the projected impacts may be marginal increases on the already large flood losses, climate change will probably have a major impact on the way in which we deal with flooding in the longer term. This especially holds true for urbanized areas in deltaic regions. Countless studies show that we should start now to adapt to climate change, to prevent costly emergency interventions in the future. This means that flood risk management strategies must meet present needs, while providing an adjustment path for the future (Pahl-Wostl, 2006; Ashley et al., 2007; Miller, 2007). For example, if governments were to take no action the UK population at risk will increase from 1.6 to 3.6 million and the cost for flood defences will increase from 3.9 to 48 million GBP by 2080 (Foresight, 2005). In developing countries the projected impacts are even worse. Particularly vulnerable are the rapid expanding mega-cities in these regions. With more than 90% of its population living in urban areas, Japan and The Netherlands are two of the most urbanized countries on earth. Urbanization and climate change are generally recognized as the major pressures inducing or intensifying floods and their impacts. Worldwide the challenge to address low probability-high impact flood risk and to reduce urban flood vulnerability has however, only recently received serious attention. This is likely because in traditional flood management approach responses to mitigate urban flood risks have been often set outside the realm of the urban system (e.g. where confined at catchment level) and responses at city level if any were predominantly passive using robust solutions such as urban defences and increasing the capacity of major culverts (Zevenbergen, 2008). In Japan, however, due to the regular occurrence of major flood events disaster relief and compensation mechanisms, damage mitigation measures specifically for urban areas have been implemented some decades ago. Transition and developing countries could learn from the lessons of Japan and from other developed countries, such as The Netherlands, which have already made the transition from agricultural to industrial, service-based economies. The first group is not yet stuck on past investments and, consequently, has greater freedom of movement.

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9.2 LEARNING FROM THE PAST Historically, natural disasters were viewed as ‘acts of God’, as disruptions to normality. Consequently, responses were directed towards managing floods as external events that affected an unknown and unprepared society (Fleuvrier, 1995). Major flood events in the past century, however, have acted as catalysts for changing policies towards floods. They have significantly increased our understanding and capacity to cope with floods. In this respect important lessons can be drawn from Japan and The Netherlands since their evolution process reveals great complexity leading to a nonstraightforward manner of progression. 9.2.1 Japan After WW II the Japanese urbanization exhibited an explosive grow, reflecting the onset of industrialization especially through a period of high economic growth from 1960 to 1973. The population migrated to cities in the downstream alluvial plains, forming mega-cities such as Tokyo and Osaka. The dike systems constructed in the past resulted in high peak flows in major rivers. As a result, when a major river dike breaches occurred along large rivers vast urban areas were flooded around the major urban centres in Tokyo, Osaka, and Nagoya. A historical example was caused by typhoon Kathleen in September 1947. This flood affected 1.6 million people, predominantly in the Tokyo Metropolitan Area. Urban floods were destructive not only in terms of economic damage, but also in terms of fatalities. A major flood disaster in a newly urbanized area was first experienced in 1958 in Tokyo-Yokohama district. This was caused by a strong typhoon known as ‘Kanogawa Typhoon’. Since then many newly urbanized areas which had no previous flood records were subjected to severe flooding, around big cities such as Tokyo, Osaka, Nagoya etc,. These floods were given the name ‘Urban Flood Disasters’, and during the 1960s and 1970s this phenomenon spread from large cities to newly developing smaller cities. On the one hand the loss of pervious areas due to urbanization has increased flood peaks and flood volumes and on the other hand the conversion of rice paddies into residential areas removed the natural retention areas, which together with improved drainage facilities shortened concentration times. This resulted in frequent urban floods as high intensity rainfalls of short duration, which are more frequent than those of long duration, could now cause floods. After 1960, the national government launched a river rehabilitation plan, including major river improvement works. The progress of ‘flood control works’ and changes in social behaviour resulted in a reduction of the number of fatalities. Better weather forecasting and early warning allowed the population to prepare for floods. However, in the three consecutive years after 1974, dike breaches of the major rivers Tama, Ishikari and Nagaramajor resulted again in devastating flood disasters. Throughout the 1960s and 1970s river-zone flood control measures such as river channel improvement, floodways, retarding basins etc., had been carried out as countermeasures against Urban Flood Disasters. However, realizing that infrastructural measures (flood defences) alone could not completely overcome the floods, an integrated approach was launched in 1977 (Ando and Takahasi, 1997) by the Ministry of Construction termed ‘Comprehensive Flood Control Measures’. This plan included temporary stormwater storage and preservation of the natural flood regulating environment as flood control

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measures to be adopted for a catchment. After about ten years, use of infiltration facilities was added to these measures. Recurrent floods continued followed by river improvement in the 1980s and 1990s. In Central Tokyo widening the river or raising higher levees were impossible as the areas along the urban rivers, especially along the Kanda River, were densely built up. The design drainage capacity could not be raised from the 50 mm/hr, which has a return period from three to five years, and engineering solutions almost reached their limits. This had led to the construction of the spectacular Kanda River Loop 7 Underground Regulation pond (started in 1988 and first phase (4.5 km long completed in 1997), a new method for an underground river – a multi-billion euro project, consisting of a pipe with a diameter of 10 to 12.5 m and dimensioned to give protection against an hourly rainfall of about 75 mm, which has a return period of once in 15 years. This has resulted in a significant decrease in the number of fatalities since the 1960s. Such efforts have greatly contributed to the decreasing trend of the economic damage (in terms of economic/GDP ratio). The main purpose of river improvement works up to then had been control of flood as efficiently as possible. These measures generally gave rise to straight and lined river channels, which were not aesthetically pleasing. At the same time a growing public concern demanded utilization of public water bodies for recreational purposes. In response, new kinds of river construction projects termed ‘Water Friendly’ projects were undertaken. These include expanding greenery and beautification of urban rivers, including aesthetically pleasing embankments, revetments designed to create a suitable environment for fish to grow, etc. Non-structural flood control measurers, such as land-use zoning, flood proofing, and flood risk mapping, as well as onsite run off control strategies for rainfall storage and infiltration facilities at individual buildings and the use of public spaces, such as parks for flood retardation were developed in line with these policy developments. Many experimental and modelling studies were conducted in the late 1980s in assessing and evaluating the effectiveness of such infiltration systems for flood control. By analyzing experimental data Herath et al. (1994) showed that converting typical drainage systems to infiltration type systems with onsite storage can result in reducing direct runoff by more than 50% in the case of urban housing schemes. Utilizing a steady state numerical simulation scheme to estimate final infiltration capacities, they developed a simplified onsite facility model that could be embedded in a urban runoff model to accurately predict runoff reduction potential from infiltration systems, thus making it possible to design such facilities in a given neighbourhood. Imbe et al. (2002) showed that such infiltration systems can perform reliably without capacity reduction even after 20 years. Studies also show that converting existing stormwater drainage to infiltration type during renovations and adopting infiltration systems in new constructions can offset adverse impacts of urbanization (Herath et al., 2003). These onsite measures were expected to contribute raising the drainage levels of beyond the 75 mm/hr level made possible by the underground river. Recent heavy rain events were experienced in the Tokyo region, causing collapse of river embankments, affecting urban functions such as transportation networks. These extreme floods were characterized as record breaking, as they have never been observed since the modernized rain gauge observations began. Although sufficient evidence is lacking of its actual manifestation, these flood events revealed Japan’s vulnerability to climate change (Ikeda, 2004). These extreme rain events have vividly shown

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the hidden vulnerability of Japanese mega cities located in flood plains. Mega cities are expanding not only in the twodimensional surface, but also vertically both upward and downward. Most of the time such expansion is carried out without adequate knowledge on the associated risks as they have not been in existence long enough to be exposed to extreme rain events that are now occurring. Especially the underground expansions are vulnerable to flooding, as witnessed in the fatal drowning cases in Japan. Most of these floods severely affected the underground railway transport systems. Two such major events in 1999 caused two fatal accidents. One was in Fukuoka, and another in Shinjuku ward in Tokyo. In both these cases, victims were drowned in underground space. Flooding in underground facilities in Tokyo are more frequent compared to other cities, which can be attributed to the high density of underground facilities located in Tokyo. The records of underground flooding in Tokyo during 1999 to 2001 identify 17 underground flooding events (Tokyo Metropolitan Government, 2002 and 2003). Most of these events occurred in summer during the period of July to September that includes the rainy season and typhoon period. There were six events in 1999, seven in 2000 and four in 2001. There was a large variation of maximum hourly rainfall during these events from 44 mm/hr to 131 mm/hr, with an average of about 60 mm/hr. A total of 17 events in Tokyo within these three years clearly show the seriousness of the underground flooding in major urban cities. According to the Japan Meteorological Agency, the average number of rainfall events per year with hourly rain intensities between 75–100 mm/hr during the period 1990 to 1997 was 17. In 1998 and 1999 there were 48 such events each year, and 16 in the year 2000. The average number of events exceeding 100 mm/hr per year during 90–97 period was just one. There were four, ten and six such events in 1998, 99 and 2000. While the linkages to global warming and rain intensity increase in Japan is not clearly established, this experience shows the necessity to prepare for the unexpected. A numerical simulation of the underground flooding of Fukuoka city (Herath and Dutta, 2005) showed the vulnerability of public facilities which tend to be located in hazard prone areas, necessity to consider multi-hazard risks where infrastructure design such as underground space doors designed to keep fires separated would aggravate underground flood impacts by preventing water spread, necessity of underground warning systems, need to map underground space and connectivity to assess risks, etc. Dynamic evolutions of cities have made them vulnerable to completely different threats compared to historical experiences. Toda et al. (2002) have investigated present day impacts of a historical flood event in Kamo River basin in Kyoto, caused by a 300 mm rainfall in 1935. By establishing a 1:30 scale model of present day underground shopping mall and the subway system, they showed that 35 tons of 100 tons of water would flow to underground space and that water would rapidly rise to about 50 cm in 20 min in the second underground level and water will accumulate to 50–100 cm in 5–10 min in the third underground level. The results clearly showed the need to have warning and guidance in underground space to steer the users of these facilities away from risk areas to safety. The experiment also showed that water would flow through the subway system to nearby stations due to elevation differences endangering commuters. A tank type model developed based on the experiments has been used to simulate various scenarios and develop mitigation measures. Based on such studies the


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Japanese government has prepared underground flood safety manuals to be used in construction and evacuation practices. The disaster mitigation policy of Japan requires taking measures to prevent recurrence of a flood that once occurred. As a result, flood control measure has been an incremental process improving infrastructure gradually to withstand ever increasing flood magnitudes. This in turn has been attracting more people and investment in flood plains. Now we are faced with the dilemma where many places have reached the limits of their ability to realistically improve flood whereas an event beyond the design levels would bring huge losses. Yet climate change threatens to increase the intensity, frequency and magnitude of storms. The time to assess the risk to people and property, especially in large urban centres, and to develop adaptive measures on that information is now. Many discussions have been taking place recently on realistic flood control approaches. Some argue that short return period should be considered and provide mechanism to make controlled flooding so that losses are minimized and flood experiences are communicated through generations. More and more attention is being placed on the possibility of using financial instruments such as risk swapping or risk spreading in order to minimize overall damage and provide means for rapid recovery. Risk assessment, especially potential loss estimation is essential to facilitate such mechanism. The flood damage estimation method in Japan has been developed in the 1950s to facilitate the economic appraisal of flood control measures. Over the years, a large number of flood damage surveys have been carried out and economic damages for the urban residential and industry categories have been established. Based on those historical data, the flood damage functions describing building and content damage in relation to flood level for both residential and industrial buildings have been established. In order to generalize the depth-damage functions, the total damage is normalized with respect to flooded floor area as well as unit cost prices established for 47 different regions. With this approach, it is possible to use the same depth-damage function throughout the country, and modify the final estimate using the unit cost for the particular region. The unit cost prices adopted are upgraded each year based on flood information and economic performance data. As this approach is officially adopted as the methodology to estimate flood damage, it is possible to use it to assess potential flood damage for a given extreme event under various scenarios if a reliable inundation modelling system is available. Dutta et al. (2000, 2006) has shown that it is possible to estimate flood damage to a fairly acceptable level using detailed GIS of properties overlain with inundation forecasts. In the future such assessments may be utilized to arrive at dynamic flood control methods to reduce losses from catastrophic flood events, and utilize financial benefits through risk swamping procedures to finance redevelopment projects that incorporate adaptive measures for reducing flood risks. In Japan, there is a now growing recognition that risks are changing over time and that it is important to identify the nature of these changes and how global warming will effect these changes. Variability and uncertainty are becoming the key issues of future Japanese flood management. Thinking in static terms of risk has shifted towards an approach where variability needs to be managed.

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9.2.2 The Netherlands The Netherlands is protected from storm surges and river floods by a reinforcement of the primary flood defence system consisting of coastal dunes, dikes and storm-surge barriers (the Delta Works). These were implemented in response to the dramatic flooding disaster in 1953 and were carried out under the so-called Delta Act. Since then, the focus has been on structural flood defences. The current flood safety standards date back to this law and include standards for maximum exceedance probability of the design of storm surge levels that dikes must sustain. A statistical approach to the storm surge levels (based on historical data) was chosen and an extrapolated storm surge level and a cost-benefit analysis formed the basis for the optimal dike height (Van Dantzig, 1956). In recent decades, the development of a new approach made it possible to assess the flood risks, taking into account the multiple failure mechanisms of a dike section and the length effect (e.g. RIVM-NMP, 2004). Only recently, Eigenraam (2003) developed a new model in which an increase of the potential damage by economic growth could be incorporated. In his model, not the exceedance probability but the expected yearly loss by flooding is taken as the central variable. These considerations have opened the discussion about a fundamental reassessment of the acceptability of the flood risks in The Netherlands, in which the (increasing) economic impacts have to taken into account. Simultaneously, scientific support was growing, which revealed that the hydraulic baseline conditions, such as storm wave properties and maximum river discharges, may be different and more severe than recently thought, and that climate change and sea-level rise may aggravate this situation. The wake-up call came in 1993 and 1995 when the rivers Meuse and Rhine almost flooded. A few years later, Hurricane Katrina in New Orleans fed the debate in The Netherlands on the limitations of the ability to control extreme events by technical means, raising increased of the possible challenges posed by the increased value of investments, population growth and climate change. Parallel to these paradigm changes, attention focused on the development of flood warning system and land use planning. Development control issues gradually received more attention in the late 1990s. In that same period, a nationally Integrated Water Management Strategy (WB21) (Room for Water, damage reduction through planning and zoning) resulted in a new policy that advocated the transition from the traditional focus on probabilities towards a more integrated approach (Tielrooij, 2000). The latter, however, is perceived as a modification of traditional practices, rather than a drastic change of direction (RIVM-NMP, 2004). The huge levels of investments and dependence on the existing defence systems in the most densely, low laying Randstad (conurbation area in Western Holland) is so high by now that options for change are limited. The inability to change is also caused by the strong interconnectivity between water institutions, management structures, routines and infrastructural entrapment. Although much emphasis is placed on the institutional integration of spatial planning and water management, the actual implementation in the Netherlands of the resulting integrated plans seems to be hampered (Van der Brugge et al., 2005). It is evident from the above that the Japanese and Dutch flood management policies have changed over time. Their transition entails a process of predominantly incremental changes and reactive responses to flood disasters or narrow escapes have acted as catalysts for accelerating this process. Major flood disasters have created the need to


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shift from flood protection to a more integrated approach and to address specifically low probability-high impacts risks (c.q. extreme events). An important observation which emerges from their history is that current flood protection measurers are based on the accumulated knowledge of past weather events: climate change is perceived as a stationary process (the past reflects the future).

9.3 CLIMATE CHANGE AND THE URBAN CONTEXT In the last decade climate change is considered as a potential trend breaker in the way that hydrological variables and existing statistical distributions on flood probabilities are addressed (e.g. Kabat et al., 2005; EEA, 2006). The present challenge seems to be that we must recognize that the future is inherently uncertain and that science will not necessarily reduce uncertainty (Neufville, 2004; Klinke and Renn, 2006). The longterm horizon of climate change and current scientific uncertainties pose special challenges. (A distinguished is usually made between epistemic and variability uncertainty. The first is due to incomplete knowledge and the second is due to inherent variability. While the epistemic uncertainty can be reduced with measurements, the variability uncertainty represents natural randomness and cannot be reduced.) Strategies which address these challenges have in common that they recognize that there is no best solution but embrace a future which fits into a distribution of events that will not come as a surprise (Rose, 2004; Pahl-Wostl, 2006). In that sense, climate change provides new incentives for the need to plan ahead and to anticipate extreme events. Cities are complex dynamic systems. Because urban floods cannot be managed in isolation they call for integrated approaches addressing multi-disciplines and different spatial scales ranging from catchment to urban communities and their interactions. We know very little about these interactions and how these interactions will affect flood impacts at city scale. Okada (2001) was one of the pioneers in this field who proposed a layer-model to identify the critical linkages (connectivity) between the different spatial layers which may be affected in a disaster. However these models are still conceptual and their use is limited to provide frameworks for identifying research. Integration infers balancing between conflicting objectives which in turn calls for an accurate assessment of the consequences of floods and how they are distributed over the different levels. In contrast to hydrological and hydraulic research, flood impact modelling at city scale is a research domain which has received little attention and their outcomes are associated with large uncertainties. The especially holds true for indirect flood loss estimation models which includes the application of Unit-Loss models, Input-Output Analysis models and the increasingly popular Computable General Equilibrium models (Veerbeek, 2007). Due to the relative novelty and complexity, the use of these models within actual case studies is so far limited. In general terms it can be stated that we tend to overestimate direct losses and underestimate indirect losses and that their spatial and temporal dimensions need still much research effort. The potentially large impact of extreme events caused by climate change further increases the urgency for an adjustment of existing assessment models and the need for appropriate vulnerability indicators which could be used to localize vulnerable ‘hotspots’. Moreover, insights in direct and indirect damage provide essential information to construct flood risk maps. These maps are becoming increasingly relevant to raise awareness

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of both policy makers and citizens to influence preparation for flooding and adaptive responses. An essential factor in successful application will be therefore, the accessibility of information for various groups of stakeholders.

9.4 LONG-TERM PLANNING Cities need to plan ahead in order to preserve or enhance their capacity to adapt proactively to rapid changes and the ability to anticipate and deal with floods. Long-term thinking calls for a new attitude. An attitude where we look beyond short-term constraints and opportunities and focus on the long-term planning horizon. There is no doubt that the long-term challenges caused by climate change will act as a catalyst to ‘mainstream’ adaptation measures into existing decision-making processes. Adapting to climate change, however, is typically a local action and the findings of national or even regional climate scenario’s and vulnerability assessments have to be downscaled to assess local potential consequences and to identify adequate responses (Pahl-Wostl, 2006). One of the challenges of assessing cities vulnerability to flood impacts is the complex and dynamic nature of the building stock. Neighbourhoods, buildings and their components are heterogeneous in their composition. Therefore as stated above high resolution data are needed to accurately assess potential flood impacts. Moreover, buildings are closely connected and integrated with other attributes in the building environment and their function as well as their physical properties may change over time. Consequently, in order to understand local impacts and their temporal changes downscaling and tailoring of existing assessment models are required that recognize the dynamic behaviour of the individual attributes of the urban fabric. Recently Veerbeek et al. (2008) conducted a detailed flood damage assessment study for the city of Dordrecht using a damage assessment model with a much higher level of detail (10 10 m grid) than was used in conventional urban flood risk assessments. These high resolution analyses revealed large differentiation in spatial and temporal distributions of expected flood damages as a function of different climate scenarios and gave important clues to identifying local adaptive responses that have the potential to become ‘mainstream’ in other decision-making processes such as substitution rates of buildings and built components. All attributes of the urban fabric require upgrades, major refurbishment and/or complete renewal. Although cities have always adapted to changing environmental conditions through autonomous adaptation, the dynamics of climate change may warrant to gradually adapting the building stock to better cope with increasing flood risk through planned retrofitting and/or re-designing its structure during its lifetime and flood resilient redevelopment. A hurdle to move to planned adaptation seems to be the paradox in present day planning practices: a timeframe of 20 years or even less is considered long-term whereas implicitly is assumed that buildings last forever and ‘site or urban location is eternal’. Planning decisions are thus typically based on specifications that assume that climate is static. Recognizing the dynamics of the urban fabric, renewal schemes of buildings may provide an opportunity to exploit substitutions of built components and structures for planned climate change adaptation. In other words: climate change adaptation should become an element in urban renewal schemes and life cycle assessments. The capacity to adapt to changing conditions depends on their substitution rates as illustrated in Figure 9.1.


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Figure 9.1 Adapting to climate change: substitution of built components and structures

9.5 FLOOD RESILIENCE The concept of resilience is often set as opposed to the traditional perspectives which attempt to control changes in systems that are assumed to be stable. This emerging concept may thus provide guidance for an overarching approach to manage urban floods which devises strategies to cope with change and uncertainty. Resilience is used quite differently in various fields. Consequently, it has a wide range of connotations. There exist however some unifying features and common notions of resilience. These are: (i) enhancing resilience is considered as a rational strategy to cope with uncertainty and surprise (ii) resilience is an internal property of (complex, dynamic) systems, (iii) resilient systems have the ability to recover from disturbance (short term response) and are able to cope with changing conditions (long term response). Hence, resilience refers to the capacity to deal with change and continue to develop (c.q. to adapt and learn). Robustness and flexibility are considered the most relevant mechanisms that enhance resilience and they stem from structural engineering. Other mechanisms have also been identified such as: diversity, connectedness, redundancy, and information feedback. Few studies have attempted to formulate systematic principles of flood resilience and applied them to flood risk management systems. An analysis to what makes river basins flood resilient and how resilience can be enhanced has been conducted by Vis and De Bruijn (2005). This theoretical work has developed three indicators. These indicators reflect the different aspects of the reaction of a system to flood waves: (1) the amplitude of the reaction, (2) the graduality of the increase of reaction with increasing disturbances and (3) the recovery rate. (The resilience of a system is larger when the amplitudes (i.e. amount of damage) are smaller, the graduality is larger or the recovery rate is higher. This means that the resilience can only be assessed by considering the whole set of indicators, and that indicators are neither to be aggregated nor prioritized. In other words, design strategies with a larger magnitude of the reaction, but with a more flat slope of the damage-frequency curve, could enhance the system resilience. This leads to less sensitivity for uncertainties in flood

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Table 9.1 Key features of the direction of the transition towards the resilient approach.

probabilities.) Despite these achievements we must conclude that at present date for the urban context there is no practical guidance as to how this concept could be made operational nor do we have a decision-making framework which provide guiding principles to formulate strategies to enhance flood resilience and to assess their efficiencies. Recently, in the context of flood risk management the precautionary approach and the adaptive approach have been recommended as a complementary approach to deal with changes and variability associated with climate change (Ashley, 2007). (Recognition of the limits of science in providing conclusive evidence has led to the adoption of the precautionary principle in decision making. Precautionary measures are aiming at increasing system’s robustness by providing passive protection and will therefore enhance system’s resilience. It must be noted that precautionary measures always require some level of proof. This knowledge condition may lead to contradictions which will hamper decision making (referred to as ‘uncertainty paradox’)). Both legitimate decisions and actions in situations where change and variability are characterized by uncertainty. The precautionary approach belongs as an attribute to changes which are not, or at least not fully, calculable and controllable, but they are within certain limits considered foreseeable (such as sea level rise). The adaptive approach is recommended for changes that are less certain by providing incremental responses as by creating flexibility. The adaptive approach enables specific decisions to be taken to alter the configuration of the system depending on the circumstances and new insights. Whether these responses are precautionary or adaptive their objectives are to actively manage and exploit uncertainty by increasing the system’s resilience. Table 9.1 gives some key features of the direction of the transition towards the resilient approach.


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9.6 EPILOGUE Japan and The Netherlands have successfully learned to cope with floods for many centuries and to adapt to changing conditions such as population growth, soil subsidence and sea level rise. Extreme weather events have triggered political responses which lead to adjustments in flood management practices and mobilized support for structural solutions. However, the interaction between climate and (urban) society is becoming more complex and societies will likely experience greater risk of getting entrapped in their institutional and technological structures. As a consequence timely and pro-active decision-making may be hampered. Long-term thinking is a prerequisite for addressing these risks and associated uncertainties which allow the capacity to adapt to new conditions to develop. However, in conventional urban planning a 20 years horizon is considered long-term and consequently most urban flood assessments focus on the consequences under static conditions of climate and building stock. In recent years there has been a growing recognition in both countries that urban flood management policies should consider the implications of these changes and that longterm infrastructural investments should comply with projected conditions imposed by climate change. This will require new approaches in urban planning and to the design of the urban fabric and emphasise the consideration of its interaction with the dynamics of its environment. Downscaling techniques are required to explore sensitivities in changes in extreme weather regimes and to develop effective adaptation strategies because extreme events occur on fine temporal and spatial scale. Planning ahead opens the way to developing strategies that are more resilient, adaptable and responsive. Japan and The Netherlands have in common that their building stock is mainly aging. European dwellings have a typical lifetime of about 50 years and in Japan of about 15 years. Continuous restructuring in both countries is common practice nowadays. These (re)development projects may provide a window of opportunity to make adjustments in the process of urban renewal in order to better cope with extreme flood events and to adapt to gradually changing conditions which enhance flood resilience.

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Index

Ackerman, Edward A, 113 Adachi Ward, 125 Akasaka, 32 Akasaka-Tameike, 32 Akihito, 17, 57, 58 Akira Inodomi, 54 Akita, 177 AMESH Rainfall Radar, 160 Ando, 94, 124, 202 Anpon, 113 Arakawa Floodway, 11, 41, 97, 98, 119, 121–124, 135 Arakawa Karyu River Office, 11, 14, 89, 93, 94, 98, 119–128, 131–139 Arakawa-Joryu River Management Office, 119 Arakawa-Karyu River Office, 19, 41, 50 Arakawa-Karyu River, 19, 41, 50 Ariake, 6, 166, 177, 178, 186, 190 Arnhem, 127 Asakusa, 30 Ashio, 107 Ayase River, 126, 132 Bakema, Jaap, 53, 54 Bakufu, 37 Bannink, 102, 128 Bay of Tokyo, 52, 63 Beppu, 19 Biwa, 66, 178 Breda, 107 Brugge, 172, 206 Building Site Preparation, 47, 81, 175 Building Standards, 37, 60, 72 Burcht, 28 Canada, 177 Carson, Dr. Rachel, 151 Chiba, 23, 59, 65, 104, 185 Chikugo River, 8, 10, 12, 97 China, 1, 60 Chinese, 19, 46

City Planning Act, 72 City Ward Improvement, 38 Climate Change, 12, 16, 82, 145, 157, 165, 172, 201, 203, 205–211 Colombia River, 12 Comprehensive Flood Control Measures, 116, 202 Comprehensive flood management, 99, 102, 119, 128, 129, 135, 139–141 Comprehensive National Development Plan, 61, 62 Comprehensive National Land Development Law, 113 Control Measures, 13, 51, 89, 97, 116, 119, 121, 152, 167, 202, 205 Control of River Water, 112 Countermeasures Act, 154 Delta Act, 206 Delta Commission, 102 Delta Works, 177, 206 Development Institute-Japan, 2, 9, 93, 98–100, 123, 125, 126, 128, 129, 138 Dike Improvement, 102 Dike Ring, 102, 135 Disaster Countermeasures Basic Act, 152 Discharge Capacity, 7, 9, 94, 122, 132, 136, 158 District Plan System, 62 Doorn, Cornelis van, 97, 103, 140 Dordrecht, 208 Dosenbori, 25 Draft City Planning Law, 39 Drainage, 3, 4, 9–12, 15, 16, 27, 30, 51, 55, 61, 95, 107, 110, 113, 136, 150, 151, 159, 176, 181, 182, 185–190, 202, 203 Dredging, 108, 136 Dutch Delta, 102, 177 Early Showa, 93 Earthquake, 4, 5, 11, 40–45, 49, 93 East China Sea, 1

222

Index

Ecological Infrastructure, 143 Ecological Quality, 15 Edo Castle, 23, 30, 72 Edo, 5, 17, 18, 21–27, 29–35, 40, 41, 44, 45, 72, 75, 95–97, 100, 103, 105–112, 114, 118, 121, 134, 151, 169 Edobashi, 33, 46 Eesteren, C. van, 55, 56 Emergency Flood Control Committee, 104 Emergency Water Services, 163 Emperor Heisei, 58 Emperor Showa, 46, 48, 57, 58 Emperor Taisho, 38, 46 England, 18, 37 Enlightened Peace, 17, 46 Environment Government of Japan, 186, 187 Environmental Systems Division, 143 European Rhine, 89 Excavation, 110, 128 Experimental Sewer System, 135, 140, 158, 159, 194 Extreme Floods, 99, 103, 115, 116, 118, 137, 145, 203 Faculty of Architecture, 17 Faculty of Civil Engineering, 119, 143, 175 Fisherman Warf, 63 Flood Control, 11, 16, 89, 91, 93, 95, 97, 99–104, 111, 112, 116, 119, 121–123, 125, 127–129, 131, 133, 135, 137–141, 143, 145, 147–150, 160, 172, 187, 190, 197, 202, 203, 205 Flood Forecasting, 98, 100, 152 Flood Hazard Maps, 98, 100 Flood Protection Act, 102, 140 Flood Protection, 11, 15, 41, 95–97, 99, 101–104, 107, 108, 110, 112, 116, 117, 119, 134, 136, 137, 140, 175, 178, 207 Flood Resilience, 209–211 Floodplains, 102, 136 Floodway, 11, 41, 97, 98, 110–112, 114, 115, 118, 119, 121–124, 132, 134–136, 151 Floor Area Ratio, 9, 57, 60, 62, 63, 65, 75, 87, 95, 104, 110, 141, 195, 207 Fluvial Flooding, 89, 100, 102, 123, 128 Fortification Act, 101, 127 Fortifications, 27, 28, 101, 127 Fukagawa, 30, 64 Fukushima Prefecture, 154 Gaikaku, 51 Garden Cities, 46 General Expansion Plan, 55, 56

General Land Use Plan, 61 German Bebauungs-Plan, 62 Ginza, 38 Golden Age, 36 Government Spatial Planning Department, 77 Great Britain, 46 Great Kanto, 11, 93 Green Urban Award, 65 Greenland, 177 Hachioji Minamino City, 65, 67 Hachioji-shi, 65 Hakata, 125 Hamacho, 25 Hamachoand Sumida, 44 Hamura, 72 Hatchobori, 30 Haussmann, 40 Hibiya, 24, 38 Hideyoshi Toyotomi, 95 Highway, 6, 33, 39, 52, 53, 61 Hikone, 9 Hirakawa River, 23, 24 Hiratani, 71 Hirohito, 17, 46, 57, 58 Hiroshima, 47 Hitachi, 105 Hohjo, 95 Hokkaido, 1, 4, 177, 187 Hokusetsu Sanda Woody Town, 70, 71 Hongo, 30 Honshu, 1, 4, 178, 187 Howard, Ebenezer, 37 Hurricane Katrina, 206 Hyoei River, 65 Hyogo, 71 Ietsuna, 30 Ieyasu, 32, 75, 95, 105 Iidamachi, 30 IJburg, 82, 83 IJssel, 92 IJsselmeer, 92 Ikari, 111 Ikenoue, 77 Imamura, 185 Imbe, 203 Immink, 102 Imperial Japanese Army, 46 Imperial Japanese Navy, 46 Imperial Palace, 25, 38 Imperial, 25, 37, 38, 46, 104 Impoldering, 177, 190 Indonesia, 177 Industrial Pollution Control Law, 152 Industrial Water Law, 185

Index Industrialization, 47–49, 98, 112, 124, 125, 127, 202 Infiltration Technology, 150, 159 Infrastructure Management, 89, 119 Inland Navigation, 92, 103–105, 112 Inogashira, 32 Inomata, 134 Institute of Technology, 143 Insurance, 146, 155, 157 Integrated Water Management Strategy, 206 Interest of Politicians, 196 International Stadium, 132 Inundation, 51, 95, 103, 113, 115, 116, 125, 129, 157, 189, 205 Inuyama, 95 IPCC, 144, 146 Isahaya Bay Reclamation, 178 Isahayawan, 177 Ise Bay Typhoon, 94 Ise Bay, 94, 99 Ise, 2, 94, 99 Isewan, 97 Ishikari River, 116 Ishikari, 99, 116, 202 Ishikawa, 177 Ishikawajima, 30, 64 Italy, 46 Jansen, P. Ph., 177 Jansz, Lucas, 28 Japan Housing Corporation, 75 Japanese Government, 104, 119, 134, 177, 205 Japanese Model, 83 Japanese National Railways Omiya, 76 Japanese Urban Planning Law, 196 Jinbunsya, 34 Jomon, 120 Joryu River Management Office, 122 Jyoganji River, 90 Kabat, 207 Kahokugata, 177 Kaish, 107–109 Kaiunbashi Bridge, 46 Kajibashi, 30 Kamo River, 204 Kanagawa Prefecture, 4, 185 Kanda River, 32, 93, 94, 203 Kanda Sewer, 151 Kanda, 30, 32, 93, 94, 151, 203 Kandadai, 25 Kandagawa River, 23, 44 Kandaogawamachi, 32 Kandayama, 24 Kanogawa, 41, 93, 94, 202

223

Kanto Earthquake, 11, 40, 93 Kanto Regional Development Bureau, 134 Karyu River, 11, 14, 89, 93, 94, 98, 119–128, 131–139 Karyu, 11, 14, 89, 93, 94, 98, 119–128, 131–139 Kasen, 116 Kasui Tosei Iinkai, 112 Kasukabe, 132 Katrina, 145, 206 Kawakami, 113 Kawamata, 111 Keihin Industrial Belt, 126 Keihin Office of Rivers, 131, 132 Keikaku, 107, 109, 111–113, 116 Keizai Antei Honbu, 113 Kema, 103 Kiguchi, 152 Kinshi Park, 44 Kinu River, 111 Kiso River, 8, 95, 96 Kitakami River, 105 Kitasenju, 125 Kitazawa River, 77, 191, 192, 198 Kobe, 38, 71 Koganei, 159 Kohriyama City, 154 Koide, 104, 105 Koishikawa, 23, 30, 32 Koji Keikaku Ikensho, 109 Kojimawan, 177 Kokai River, 110, 111 Kondo, S., 109 Koshigaya City, 185 Kosui Koji Keikaku Ikensho, 107 Koto Ward, 185 Kozukue, 131 Kuge Canal, 121 Kumagaya, 121 Kundzewicz, 99, 123, 125 Kuramatsu River, 134 Kurihashi, 93, 113 Kyobashi, 30 Kyu, 1 Kyushu, 4, 125, 186 Lake Nakaumi, 187 Lake Shinji, 187 Land Development Corporation, 75 Land Planning System, 60 Land Readjustment District, 42 Land Use, 1, 13, 18, 39, 48, 51, 60, 61, 72, 73, 145, 179, 206 Landfill, 25, 31, 129, 179 Late Meiji, 93 Late Showa, 99

224

Index

Le Corbusier, 52 Leiden, 28 Leurs, 144 Lindo, Isaac, 107, 108 Lobith, 113 Local Autonomy Agency, 49 Lowland Technology, 175 Lowlands, 2, 6, 10, 16, 24, 41, 51, 95, 122, 175, 190 Machizukuri, 62, 71, 72, 83 Maeda, 126 Makuhari Messe, 65 Makurazaki, 97 Malaysia, 1 Manchuria, 46 Marunouchi, 38, 65 Matsuda Osamu, 35 Matsuo Basho, 8 Matsuura, 104, 112 Matsuzaki, 116, 117 Meiji Constitutions, 38 Meiji Era, 18, 97, 177 Meiji Government, 46, 97 Meiji Restoration, 18, 43, 190 Meteorological Agency, 204 Metropolitan Daiba Park, 65 Metropolitan Government, 15, 72, 77, 87, 113, 131, 139, 150, 152, 153, 157–159, 161, 162, 164, 169, 204 Metropolitan Outer Floodway, 132, 134, 151 Meuse, 102 Mid Showa, 86, 97 Mikawahima Sewer Treatment Plant, 151 Minamata-disease, 151 Ministerial Agency of Environment, 60 Ministry of Agriculture, 179, 187 Ministry of Environment, 75 Ministry of Interior, 104, 112, 113 Ministry of Transport, 136 Mitigation Measures, 11, 99, 119, 128, 129, 134, 141, 150, 201, 204 Mitsui Fudosan Group, 64 Mononobe, 112 Montana, 1 Motoyama, 161 Motoyoshi, 94 Mount Asama, 106 Mount Fuji, 157 Mount Kobushigatake, 119 Multi-Purpose Dam Construction Act, 160 Municipal Master Plan, 72 Muromachi, 121 Musashi Canal, 121 Musashino-shi, 74, 76 Nagaoka University of Technology, 191

Nagara River, 116 Nagara, 99, 116 Nagaramajor, 202 Nagasaki, 47, 99, 177, 178 Naguri, 41, 122 Naha Shin Toshin, 68, 69 Naha-shi, 68 Naimusho, 39 Naka River, 126, 132, 134 Naka, 126, 132, 134, 151 Nakabashi, 35 Nakagawa, 122 Nakaumi Lake, 179 Nakaumi, 179, 187 NakaumiShinjiko, 177 Nara, 25, 121 National Land Agency, 60 National Land Use Agency, 61 National Land Use Guideline, 61 National Land Use Planning Law, 60 National Resources Planning Board, 113 Naturnaher Wasserbau, 86 New Babylon, 53 New City Plan Act, 154 New City Planning Law, 50, 58 New Orleans, 145, 206 New Town Act, 50 New Town, 49, 50, 62, 159, 160, 175 New York, 64 New Zealand, 1 Nihonbashi Bridge, 6, 32, 44 Nihonbashi River, 23, 44 Niigata Prefecture, 9 Niigata, 9, 95, 185 Nijmegen, 127, 192, 198, 199 Nippon, 104 North Sea, 91, 92 North-West Honshu, 178 Ochiai Treatment Plant, 152 Ochiishi, 187 Odaiba Sea Park, 63 Ohotoshi-no-furutone River, 134 Oji, 93, 109 Okada, 207 Okawabata, 64, 139 Okayama, 177 Okinawa Prefecture, 68 Okinawa, 1, 46, 68 Okubo Togoro, 32 Omiya, 76 Omura, 1, 90 Osaka Airport, 6 Osaka Bays, 2 Osdorp, 56, 57 Ota Do, 23

Index Otemachi, 125 Otsu City, 66 Otsu, 66, 68 Otsu-shi, 66 Pacific Belt Region, 48, 51, 61 Pacific Ocean, 90, 96, 104 Pacific War, 18, 46 Pampus, 53, 54 Paris, 40 Plan Pampus, 53 Plan Zuid Amsterdam, 47, 48 Planning Act, 40, 41, 49, 72 Pluvial Flooding, 89, 123, 128, 147, 152, 155, 167, 169 Polder, 1, 27, 35–37, 55, 57, 82, 86, 148, 175, 177–180 Pollution Diet, 60 Pollution, 2, 4, 13, 15, 16, 49, 50, 60, 62, 98, 107, 116, 121, 143, 152, 175, 191, 195 Potsdam Declaration, 46 Precipitation, 2, 7, 8, 10, 91, 94, 98, 122, 135, 139, 152, 160, 188, 189 Project Spankrachtstudie, 102, 122, 123, 129, 130, 132, 135 Protection Act, 102, 140 Railway, 18, 36, 46, 48, 49, 86, 94, 104, 121, 122, 134, 204 Rainwater Infiltration Facilities, 159 Rainwater Storage, 150, 159, 197 Randstad, 206 Reconstruction Board, 40 Reconstruction Bureau, 40 Regional Development Corporation, 76 Renaissance Agency, 65, 67–71, 74–77 Resources Board, 113 Retarding Basin, 109, 110 Rhine River, 10, 89 Rhine, 91, 140 Rijke, Johannis de, 97, 140 Rindo Nihon, 107 River Act, 86, 137 River Association, 2, 9, 93, 98–100, 123, 125, 126, 128, 129, 138 River Improvement Plan, 86, 117 Roppongi, 34, 65 Rose, W.N. 36, 48, 51, 207 Rotterdam, 27, 36, 82, 125 Rouwenhorst Mulder, A. Th. L., 107 Russia, 1 Saitama Hiroba, 76 Saitama Shintoshin, 76 Saitama Super Arena, 76

225

Saitama-shi Saitama Perfecture, 76 Sakai-machi, 103, 107 Sakamaki, 106 Sakamaki-Setoi, 106, 109 Sakurabashi, 64 Sanbumachi, 185 Sanda International Park City, 71 Sanda-shi, 71 Sato, 94, 117 Sea of Japan, 1, 90 Sengawa River, 76 Sengoku, 95 Setagaya Machizukuri Ordinance, 62 Seto Inland Sea, 90 Setoi, 106 Severe Disaster Relief Act, 9 Sewage Treatment, 10, 72 Sewer System, 13, 51, 135, 140, 151–153, 158, 159, 194 Sewerage Mapping, 160 Shakujii River, 158 Shibaura, 64, 151 Shibuya, 34 Shiga Prefecture, 66, 75 Shigen Iinkai, 113 Shikoku, 1 Shimane, 177 Shimbashi, 25 Shimofusa, 23 Shimokobe Atsushi, 61 Shinegawa, 64 Shinjuku, 34, 204 Shinkawa River, 94 Shiodome, 65, 167 Shirako River, 158 Shitamachi, 5, 25 Sho- wa Emperor, 17 Sho- wa, 17, 18, 46, 48, 58 Sino-Japanese War, 46 Soil Mechanics, 47, 81 Spatial Planning Department of Tokyo, 139 Special Planning Act, 49 Sprawl, 46, 57–59, 61, 86 St. Petersburg, 5 Stabilization Board, 113 Staets, Hendrik Jackobzn, 28 Statistics Bureau of Japan, 124, 125 Stichting Architecture Research, 53 Stormwater, 7, 13, 15, 16, 69, 71, 124, 131, 132, 135, 143, 145, 147, 149, 151–155, 157, 159, 161, 163, 165–169, 171–173, 175, 191, 192, 194–197, 202, 203 Subsidence, 51, 81, 127, 147–150, 152, 160, 172, 175, 177, 180–182, 184–187, 195, 211 Suetsugi, 131

226

Index

Sun Varie Sakurazutsumi, 74, 76 Super Levee, 77, 86, 87, 99, 119, 136–140 Surugadai, 30 Sustainable Development Programme, 201 Sustainable Urban Infrastructure, 201 Switzerland, 86 Taisho, 38, 46, 93 Taiwan, 1 Takenaka Corporation, 139 Tama River Improvement Plan, 86 Tama River, 75 Tamagawa Canal, 72 Tamagawa, 32, 72 Tamai, 116, 117 Tan, 19, 21, 23, 61 Tange, Kenzo, 52–54 Tashizengata, 116 Tatano, 157 Technopolis, 62, 65 Tennessee River, 12 Tennessee Valley Authority, 61, 112 Tohno, 185 Tokai Flood of September, 125 Tokai, 94, 95, 125 Tokiwabashi, 30 Tokugawa Ieyasu, 105 Tokugawa Japan, 84 Tokugawa Shogunate, 65, 95, 96, 106 Tokyo Bureau of Sewerage, 154 Tokyo City Improvement Ordinance, 38 Tokyo City Sewerage Plan, 151 Tokyo Metropolitan Area, 9, 93, 119, 124, 126, 129, 161–163, 202 Tokyo Metropolitan Basic Plan, 76 Tokyo Rainfall Radar System, 160 Tokyo Station, 38, 42 Tokyo Teleport Town, 65, 66 Tokyo-Yokohama, 202 Tominaga, 109, 111, 112 Tone Canal, 111 Tone, 23 Tonegawa Chisui Senmon Iinkai, 110 Tonegawa Floodway, 112, 114, 115, 118 Tonegawa Kaitei Kaish-u Keikaku, 113 Tonegawa Zoho Keikaku, 111, 112 Tonem, 110 Toriyama, 131 Tottori, 177 Town Planning Act, 40, 41 Toyokawa River, 8 Tskuba, 62 Tsukishima, 64 Tsukuba, 65, 89, 119 Tsukudajima, 30 Tsumaki Yorinaka, 44

Tsumanuma, 107 Tsurumi River Basin, 4, 5, 93, 94, 126 Tsurumi River, 4, 5, 93, 94, 126, 129, 131 Typhoon Ise Bay, 99 Typhoon Ise-wan, 152 Typhoon Kanogawa, 93, 94 Typhoon Kathleen, 9, 93, 97, 125, 202 Typhoon, 2, 9, 27, 41, 93, 94, 97, 99, 111, 113, 116, 120, 125, 152, 202, 204 Uekusa, 185 United States, 18, 46, 112, 151 Unno, 126 Urban Building Law, 39, 50 Urban Design, 17, 18, 36, 44, 47, 55, 57, 75, 78, 81, 82, 85–87, 165, 175 Urban Development, 4, 6, 18, 49, 51, 53, 60, 62, 75, 76, 84, 121, 139, 154, 160, 162, 170, 175, 191, 197 Urban Drainage, 4, 10, 15, 187, 189, 190 Urban Expansion, 17, 55 Urban Flood Disasters, 100, 202 Urban Growth, 21, 22, 37, 38, 48, 86, 122, 167 Urban Planning, 17, 18, 21, 25, 37, 39, 71, 72, 138, 143, 196, 211 Urban Promotion Area, 58 Urban Redevelopment Law, 60 Urban Renaissance, 65, 67–71, 74–77 Urban River Basins, 100, 157 Urban River Inundation Damage Countermeasure Act, 157 Urban Water Infrastructure, 143, 169 Urban Water Management, 1, 16, 135, 169, 175, 191, 193, 195, 197, 199 Urbanization, 2, 4, 7, 8, 15, 16, 20, 21, 27, 41, 47–49, 58, 60, 62, 89, 93, 98, 99, 115, 119, 121, 123, 124, 126–129, 131, 140, 143, 145, 147, 149, 150, 152, 157, 158, 165, 167, 172, 201–203 Utrecht, 81 Venice, 5, 26, 27 Waal, 140 Wada-Yoshino-Iruma, 121 Watarase River, 107, 109 Watarase, 107, 109–111 Water Board, 82 Water Management, 1, 16, 17, 21, 27, 28, 37, 41, 47, 55, 81, 82, 85–87, 101–103, 106, 107, 110, 112, 113, 115, 116, 118, 135, 148, 157, 165, 169, 172, 175, 191, 193, 195, 197, 199, 206 Water Pollution Control Law, 60

Index Water Pollution Law, 121 Water Project, 36, 55 Water Resources Development Promotion Act, 160 Water Storage, 55, 127, 129, 135, 154, 170, 172 Water Test, 82 Water Works, 38 Waterfront Sub Center Plan, 65, 66 Waterfront Town Development, 66 Waterfront, 13, 30–33, 41, 44, 45, 64–66, 71, 76 Watersupply Tokyo, 33 Watertoets, 82 Willamette River, 12 World War I, 112 World War II, 46, 56, 93, 97, 112, 113, 143, 175, 177, 185, 190

Yamanote, 5, 31 Yanaka, 109 Yayoi, 121 Yodo River, 11, 95, 97, 103, 119 Yodo, 11, 95, 97, 103, 119 Yodogawa River, 8 Yokohama City, 185 Yonemoto, 31 Yoroibashi, 46 Yoshimoto, 131 Yoshino, 8 Yoshitani, 2, 98, 100 Yushima, 30 Zocher, J. D. and L.P, 36

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