Stormwater Effects Handbook: A Toolbox for Watershed Managers,Scientists,and Engineers

Stormwater Effects Handbook A Toolbox for Watershed Managers, Scientists, and Engineers

Stormwater Effects Handbook A Toolbox for Watershed Managers, Scientists, and Engineers G. Allen Burton, Jr., Ph.D.

Robert E. Pitt, Ph.D., P.E.

LEWIS PUBLISHERS A CRC Press Company

Boca Raton London New York Washington, D.C.

Library of Congress Cataloging-in-Publication Data

Burton, G. Allen Stormwater effects handbook : a toolbox for watershed managers, scientists, and engineers / by G. Allen Burton, Jr. and Robert Pitt. p. cm. Includes bibliographical references and index. ISBN 0-87371-924-7 (alk. paper) 1. Runoff—Management—Handbooks, manuals, etc. 2. Runoff—Environmental aspects—Handbooks, manuals, etc. 3. Water quality—Measurement—Handbooks, manuals, etc. 4. Water quality biological assessment—Handbooks, manuals, etc. I. Pitt, Robert. II. Title. TD657 .B86 2001 628.1'68—dc21

2001029906 CIP

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Dedication This book is dedicated to those who were instrumental in guiding and supporting our develop­ ment as scientists and engineers and our appreciation of the outdoors.

Preface This handbook is intended to be a working document which assists scientists, engineers, consultants, regulators, citizen groups, and environmental managers in determining if stormwater runoff is causing adverse effects and beneficial-use impairments in local receiving waters. This includes adverse effects on aquatic life and human health and considers exposures to multiple stressors such as pathogens, chemicals, and habitat alteration. Given the complicated nature of the problem, where diffuse inputs contain multiple stressors which vary in intensity with time (and often in areas which are simultaneously impacted by point source discharges or other development activities, e.g., channelization), it is difficult to define and separate stormwater effects from these other factors. To accomplish this task requires an integrated watershed-based assessment approach which focuses on sampling before, during, and after storm events. This handbook provides a logical approach for an experimental design that can be tailored to address a wide range of environmental concerns, such as ecological and human health risk assess­ ments, determining water quality or biological criteria exceedances, use impairment, source iden­ tification, trend analysis, determination of best management practice (BMP) effectiveness, stormwater quality monitoring for NPDES Phase I and II permits and applications, and total maximum daily load (TMDL) assessments. Despite the complexity of stormwater, successful and accurate assessments of its impact are possible by following the logical integrated approaches described in this handbook. New methods and technologies are rapidly being developed, so this should be considered a “living” document which will be updated as the science warrants. We welcome your input on ways to improve future editions. Allen Burton Bob Pitt May 2001

Disclaimer: The views presented within this document do not necessarily represent those of the U.S. Environmental Protection Agency.

Acknowledgments We are indebted to our professional colleagues whose prior contributions enabled us to produce this book. In addition, the long productive hours of a host of graduate and undergraduate students at Wright State and the University of Alabama at Birmingham are acknowledged for their essential research contributions. We greatly appreciate the word processing of Nancy Pestian and Amy Ray. We also thank the production staff and editors at Lewis Publishers/CRC Press for their hard work and patience. The support of the U.S. EPA, especially Richard Field, is also appreciated, not only for help in the preparation of this current work, but also for the prior support given to many of the research projects described in this book. Special thanks are also due to our families, who provided never-ending support during the preparation of this book.

About the Authors G. Allen Burton, Jr., is the Brage Golding Distinguished Professor of Research and Director of the Institute for Environmental Quality at Wright State University. He obtained a Ph.D. degree in Environmental Science from the University of Texas at Dallas in 1984. From 1980 until 1985 he was a Life Scientist with the U.S. Environmental Protection Agency. He was a Postdoctoral Fellow at the National Oceanic and Atmo­ spheric Administration’s Cooperative Institute for Research in Environ­ mental Sciences at the University of Colorado. Since then, he has had positions as a NATO Senior Research Fellow in Portugal and Visiting Senior Scientist in Italy and New Zealand. Dr. Burton’s research during the past 20 years has focused on devel­ oping effective methods for identifying significant effects and stressors in aquatic systems where sediment and stormwater contamination is a concern. His ecosystem risk assessments have evaluated multiple levels of biological organization, ranging from microbial to amphibian effects. He has been active in the development and standard­ ization of toxicity methods for the U.S. EPA, American Society for Testing and Materials (ASTM), Environment Canada, and the Organization of Economic Cooperation and Development (OECD). Dr. Burton has served on numerous national and international scientific committees and review panels, and written more than 100 publications dealing with aquatic systems. Robert Pitt is currently a Professor in the Department of Civil and Environmental Engineering at the University of Alabama. Bob had pre­ viously served on the School of Engineering faculty at the University of Alabama at Birmingham since 1987. Prior to that, he was a Senior Engi­ neer for 16 years in industry and government, and continues to consult to many municipalities and engineering firms. He received his Ph.D. in Civil and Environmental Engineering from the University of Wiscon­ sin–Madison, his M.S.C.E. in Environmental Engineering/Hydraulic Engineering from San Jose State University, CA, and his B.S. in Engi­ neering Science, from Humboldt State University, Arcata, CA. He is a registered professional engineer (WI) and a Diplomate of the American Academy of Environmental Engineers. During the past 30 years, Bob has been the project manager and principal investigator for many water resources research projects conducted for the U.S. EPA, Environment Canada, Ontario Ministry of the Environment, and state and local governments concerning the effects, sources, and control of urban runoff. Some are used as case studies in this book. His major area of interest is in stormwater management, especially the integration of drainage and water quality objectives. He currently teaches classes in water supply and drainage design, hydrology, hydraulics, experimental design, and field sampling, plus a series on stormwater man­ agement. Bob has published more than 100 chapters, books, journal articles, and major research reports. He is a member of the American Society of Civil Engineers, the Water Environment Federation, the North American Lake Management Society, the American Water Resources Asso­ ciation, and the Society for Environmental Toxicology and Chemistry.

Contents Unit 1: The Problem of Stormwater Runoff Chapter 1 Introduction Overview: The Problem of Stormwater Runoff ......................................................................3

Sources of NPS Pollution.........................................................................................................4

Regulatory Program..................................................................................................................8

Applications of the Handbook ...............................................................................................10

References ........................................................................................................................................13

Chapter 2 Receiving Water Uses, Impairments, and Sources of Stormwater Pollutants Introduction.............................................................................................................................15

Beneficial Use Impairments ...................................................................................................22

Likely Causes of Receiving Water Use Impairments............................................................30

Major Urban Runoff Sources.................................................................................................31

Summary.................................................................................................................................42

References ........................................................................................................................................43

Chapter 3 Stressor Categories and Their Effects on Humans and Ecosystems Effects of Runoff on Receiving Waters .................................................................................47

Stressor Categories and Their Effects....................................................................................63

Receiving Water Effect Summary..........................................................................................90

References ........................................................................................................................................92

Unit 2: Components of the Assessment Chapter 4 Overview of Assessment Problem Formulation Introduction...........................................................................................................................102

Watershed Indicators of Biological Receiving Water Problems .........................................103

Summary of Assessment Tools ............................................................................................107

Study Design Overview........................................................................................................107

Beginning the Assessment....................................................................................................108

Example Outline of a Comprehensive Runoff Effect Study ...............................................119

Case Studies of Previous Receiving Water Evaluations......................................................123

Summary: Typical Recommended Study Plans...................................................................213

References ......................................................................................................................................218

Chapter 5 Sampling Effort and Collection Methods Introduction...........................................................................................................................224

Experimental Design: Sampling Number and Frequency ...................................................224

Data Quality Objectives (DQO) and Associated QA/QC Requirements ............................247

General Considerations for Sample Collection ...................................................................254

Receiving Water, Point Source Discharge, and Source Area Sampling..............................278

Sediment and Pore Water Sampling ....................................................................................313

Summary: Basic Sample Collection Methods .....................................................................336

References ......................................................................................................................................338

Chapter 6 Ecosystem Component Characterization Overview...............................................................................................................................346

Flow and Rainfall Monitoring..............................................................................................349

Soil Evaluations....................................................................................................................388

Aesthetics, Litter, and Safety ...............................................................................................398

Habitat...................................................................................................................................400

Water and Sediment Analytes and Methods ........................................................................423

Microorganisms in Stormwater and Urban Receiving Waters ............................................485

Benthos Sampling and Evaluation in Urban Streams .........................................................491

Zooplankton Sampling .........................................................................................................502

Fish Sampling.......................................................................................................................502

Toxicity and Bioaccumulation .............................................................................................507

Summary...............................................................................................................................546

References ......................................................................................................................................550

Chapter 7 Statistical Analyses of Receiving Water Data Selection of Appropriate Statistical Analysis Tools and Procedures ..................................575

Comments on Selected Statistical Analyses Frequently Applied to Receiving Water

Data.......................................................................................................................................582

Summary of Statistical Elements of Concern When Conducting a Receiving Water

Investigation..........................................................................................................................605

References ......................................................................................................................................606

Chapter 8 Data Interpretation Is There a Problem? .............................................................................................................609

Evaluating Biological Stream Impairments Using the Weight-of-Evidence Approach ......611

Evaluating Human Health Impairments Using a Risk Assessment Approach....................619

Identifying and Prioritizing Critical Stormwater Sources ...................................................626

Summary...............................................................................................................................636

References ......................................................................................................................................637

Unit 3: Toolbox of Assessment Methods Appendix A Habitat Characterization The Qualitative Habitat Evaluation Index (QHEI) .............................................................643

The USEPA Habitat Assessment for the Rapid Bioassessment Protocols..........................652

References.............................................................................................................................662

Appendix B Benthic Community Assessment Rapid Bioassessment Protocol: Benthic Macroinvertebrates .............................................665

The Ohio EPA Invertebrate Community Index Approach .................................................681

A Partial Listing of Agencies that Have Developed Tolerance Classifications and/or

Biotic Indices........................................................................................................................687

References ......................................................................................................................................690

Appendix C Fish Community Assessment Rapid Bioassessment Protocol V — Fish ...........................................................................693

References ......................................................................................................................................707

Appendix D Toxicity and Bioaccumulation Testing General Toxicity Testing Methods .......................................................................................710

Methods for Conducting Long-Term Sediment Toxicity Tests with Hyalella azteca ........710

Methods for Conducting Long-Term Sediment Toxicity Tests with Chironomus

tentans...................................................................................................................................718

In Situ Testing Using Confined Organisms .........................................................................724

Toxicity Identification Evaluations ......................................................................................729

Toxicity — Microtox Screening Test...................................................................................730

References ......................................................................................................................................733

Appendix E Laboratory Safety, Waste Disposal, and Chemical Analyses Methods Introduction...........................................................................................................................736

Fundamentals of Laboratory Safety.....................................................................................737

Basic Rules and Procedures for Working with Chemicals..................................................738

Use and Storage of Chemicals in the Laboratory ...............................................................743

Procedures for Specific Classes of Hazardous Materials ....................................................748

Emergency Procedures .........................................................................................................758

Chemical Waste Disposal Program ......................................................................................760

Material Safety Data Sheets (MSDS) ..................................................................................763

Summary of Field Test Kits .................................................................................................767

Special Comments Pertaining to Heavy Metal Analyses ....................................................774

Stormwater Sample Extractions for EPA Methods 608 and 625........................................779

Calibration and Deployment Setup Procedure for YSI 6000upg Water Quality

Monitoring Sonde.................................................................................................................782

References ......................................................................................................................................785

Appendix F Sampling Requirements for Paired Tests Charts....................................................................................................................................787

Appendix G Water Quality Criteria Introduction...........................................................................................................................798

EPA’s Water Quality Criteria and Standards Plan — Priorities for the Future ..................798

Compilation of Recommended Water Quality Criteria and EPA’s Process for Deriving

New and Revised Criteria ....................................................................................................799

Ammonia ..............................................................................................................................813

Bacteria .................................................................................................................................816

Chloride, Conductivity, and Total Dissolved Solids............................................................822

Chromium .............................................................................................................................823

Copper...................................................................................................................................824

Hardness ...............................................................................................................................825

Hydrocarbons........................................................................................................................826

Lead ......................................................................................................................................827

Nitrate and Nitrite ................................................................................................................828

Phosphate..............................................................................................................................830

pH .........................................................................................................................................832

Suspended Solids and Turbidity...........................................................................................834

Zinc .......................................................................................................................................835

Sediment Guidelines.............................................................................................................836

References ......................................................................................................................................839

Appendix H Watershed and Receiving Water Modeling Introduction...........................................................................................................................843

Modeling Stormwater Effects and the Need for Local Data for Calibration and

Verification............................................................................................................................845

Summary...............................................................................................................................860

References ......................................................................................................................................866

Appendix I

Glossary.................................................................................................................867

Appendix J Vendors of Supplies and Equipment Used in Receiving Water Monitoring General Field and Laboratory Equipment ...........................................................................871

Automatic Samplers .............................................................................................................872

Basic Field Test Kits ............................................................................................................873

Specialized Field Test Kits...................................................................................................873

Parts and Supplies for Custom Equipment ..........................................................................873

Toxicity Test Organisms.......................................................................................................874

Laboratory Chemical Supplies (and other equipment)........................................................874

Index ..............................................................................................................................................875

UNIT 1

The Problem of Stormwater Runoff

CHAPTER

1

Introduction “A stench from its inky surface putrescent with the oxidizing processes to which the shadows of the over-reaching trees add stygian blackness and the suggestion of some mythological river of death. With this burden of filth the purifying agencies of the stream are prostrated; it lodges against obstructions in the stream and rots, becoming hatcheries of mosquitoes and malaria. A thing of beauty is thus transformed into one of hideous danger.” Texas Department of Health 1925

CONTENTS Overview: The Problem of Stormwater Runoff ................................................................................3 Sources of NPS Pollution ..................................................................................................................4 Regulatory Program ...........................................................................................................................8 Applications of the Handbook.........................................................................................................10 Stormwater Management Planning (Local Problem Evaluations and Source Identifications) ........................................................................................................................10 Risk Assessments ...................................................................................................................11 Total Maximum Daily Load (TMDL) Evaluations ...............................................................11 Model Calibration and Validation ..........................................................................................11 Effectiveness of Control Programs ........................................................................................12 Compliance with Standards and Regulations ........................................................................13 References ........................................................................................................................................13

OVERVIEW: THE PROBLEM OF STORMWATER RUNOFF The vivid description, above, of the Trinity River as it flowed through Fort Worth and Dallas, TX, in 1925 is no longer appropriate. The acute pollution problems that occurred in the Trinity River and throughout the United States before the 1970s have been visibly and dramatically improved. The creation of the U.S. Environmental Protection Agency (EPA) and the passage of the Clean Water Act (CWA) in 1972 resulted in improved treatment of municipal and industrial wastewaters, new and more stringent water quality criteria and standards, and an increased public awareness of water quality issues. During the first 18 years of the CWA, regulatory efforts, aimed at pollution control, focused almost entirely on point source, end-of-pipe, wastewater discharges. However, during this same period, widespread water quality monitoring programs and special studies conducted by state and federal agencies and other institutions implicated nonpoint sources

3

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STORMWATER EFFECTS HANDBOOK

(NPS) as a major pollutant category, affecting most degraded waters around the country. For example, in Ohio 51% of the streams assessed were thought to be adversely impacted by NPS pollution. Nonpoint source pollution presents a challenge from both a regulatory and an assessment perspective. Unlike many point source discharges, pollution inputs are not constant, do not reoccur in a consistent pattern (i.e., discharge volume and period), often occur over a diffuse area, and originate from watersheds whose characteristics and pollutant loadings vary through time. Given this extreme heterogeneity, simple solutions to NPS pollution control and the assessment of eco­ system degradation are unlikely. Fortunately, methods do exist to accomplish both control and accurate assessments quite effectively. To accomplish this, however, one must have a clear understanding of the nature of the problem, the pollutant sources, the receiving ecosystem, the strengths and weaknesses of the assessment tools, and proper quality assurance (QA) and quality control (QC) practices. This handbook will discuss these issues as they pertain to assessing stormwater runoff effects on freshwater ecosystems.

SOURCES OF NPS POLLUTION A wide variety of activities and media comprise NPS pollution in waters of the United States (Table 1.1). The major categories of sources include agriculture, silviculture, resource extraction, hydro-modification, urban areas, land disposal, and contaminated sediments. The contribution of each category is, of course, a site-specific issue. In Ohio, as in many midwestern and southern states, agriculture is the principal source of NPS stressors, as shown in Table 1.2 (ODNR 1989). These stressors include habitat destruction (e.g., channelization, removal of stream canopy and riparian zone, loss of sheltered areas, turbidity, siltation) and agrichemicals (e.g., pesticides and nutrients). In urban areas, stream and lake impairment is also due to habitat destruction; but, in addition, physical and chemical contaminant loadings come from runoff from impervious areas (e.g., parking lots, streets) of construction sites, and industrial, commercial, and residential areas. Numerous studies (such as May 1996) have examined the extent of urbanization in relation to decaying receiving water conditions (Figure 1.1). Other contaminant sources that have been docTable 1.1 Nonpoint Source Pollution Categories and Subcategories Category: Agriculture General agriculture Crop production Livestock production Pasture Specialty crop production Category: Silviculture General silviculture Harvesting, reforestation Residue management Road construction Forest management Category: Resource Extraction General resource extraction Surface coal mining Subsurface coal mining Oil/Gas production Category: In-place (Sediment) Pollutants

Category: Hydromodification General hydromodification

Channelization

Dredging

Dam construction

Stream bank modification

Bridge construction

Category: Urban General urban Storm sewers Sanitary sewers Construction sites Surface runoff Category: Land Disposal General land disposal

Sludge disposal

Wastewater

Sanitary landfills

Industrial land treatment

On-site wastewater treatment

From EPA. Results of the Nationwide Urban Runoff Program. Water Planning Division, PB 84-185552, Washington, D.C. December 1983.

INTRODUCTION

5

Table 1.2 Major Categories of Nonpoint Source Pollution Impacting Surface Water Quality in Ohio Major Categories of Nonpoint Source Pollution

Stream Miles Affected

Percentage of Miles Affected

Agriculture Resource extraction Land disposal Hydromodification Urban Silviculture In-place pollutants Total stream miles affected

5300 2000 1600 1500 1100 400 100 12,000

44 17 13 13 9 3 1

From ODNR (Ohio Department of Natural Resources). Ohio Nonpoint Source Management Program. Ohio Department of Natural Resources, Columbus, OH. 1989.

Figure 1.1 0 Relationship between basin development, riparian buffer width, and biological integrity in Puget Sound lowland streams. (From May, C.W. Assessment of the Cumulative Effects of Urbanization on Small Streams in the Puget Sound Lowland Ecoregion: Implications for Salmonid Resource Management. Ph.D. dissertation, University of Washington, Seattle. 1996. With permission.)

umented, but are even more difficult to assess, include accidental spills, unintended discharges, and atmospheric deposition. The pollutants present in stormwater runoff vary with each watershed; however, certain pollut­ ants are associated with specific activities (e.g., soybean farming, automobile service areas) and with area uses (e.g., parking lots, construction). By analyzing the land use patterns, watershed characteristics, and meteorological and hydrological conditions, an NPS assessment program can be focused and streamlined. A number of studies have linked specific pollutants in stormwater runoff with their sources (Table 1.3). Pitt et al. (1995) reviewed the literature on stormwater pollutant sources and effects and also measured pollutants and sample toxicity from a variety of urban source categories of an impervious and pervious nature. The highest concentrations of synthetic organics were in roof runoff, urban creeks, and combined sewer overflows (CSOs). Zinc was highest from roof runoff (galvanized gutters). Nickel was highest in runoff from parking areas. Vehicle service areas produced the highest cadmium and lead concentrations, while copper was highest in urban creeks (Pitt et al. 1995). Most metals in stormwater runoff originate from streets (Table 1.4, FWHA 1987) and parking areas. Other metal sources include wood preservatives, algicides, metal corrosion, road salt, bat­ teries, paint, and industrial electroplating waste. One large survey (EPA 1983) found only 13 organics occurring in at least 10% of the samples. The most common were 1,3-dichlorobenzene

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STORMWATER EFFECTS HANDBOOK

Table 1.3 Potential Sources of Stormwater Toxicants Automobile Use

Pesticide Use

Industrial/Other

Halogenated Aliphatics Methylene chloride Methyl chloride

Leaded gas

Fumiganta Fumiganta

a

Plastics, paint remover, solvent Refrigerant, solvent

Phthalate Esters Di-N-butyl phthalate

Insecticide

Bis (2-ethyhexyl) phthalate Butylbenzyl phthalate

Plasticizera, printing inks, paper, stain, adhesive Plasticizera Plasticizera

Polycyclic Aromatic Hydrocarbons Chrysene Phenanthrene Pyrene

Gasolinea, oil/grease

Gasoline

Gasoline, oil, asphalt

Wood/coal combustiona Wood preservatives Wood/coal combustiona Volatiles

Benzene

Gasolinea Insecticide

Chloroform Toluene

Gasolinea, asphalt

Solvent formed from salt, gasoline and asphalt Solvent, formed from chlorinationa Solvent

Heavy Metals Chromium

Metal corrosiona

Copper

Metal corrosion, brake linings Gasoline, batteries Metal corrosion, road salt, rubbera

Lead Zinc

Algicide

Wood preservative

Paint, metal corrosion, electroplating wastea Paint, metal corrosion, electroplating wastea Paint

Paint, metal corrosiona

Organochlorides and Pesticides Lindane Chlordane Pentachlorophenol PCBs

Mosquito controla Seed pretreatment Termite controla Wood preservative

Paint

Wood processing

Electrical, insulation, paper

adhesives

Dieldrin Diazinon Chlorpyrifos Atrazine a

Most significant sources. Modified from Callahan, M.A., et al., Water Related Environmental Fates of 129 Priority Pollutants. U.S. Envi­ ronmental Protection Agency, Monitoring and Data Support Division, EPA-4-79-029a and b. Washington D.C. 1979; Verschueren, K. Handbook of Environmental Data on Organic Chemicals, 2nd edition. Van Nostrand Reinhold Co., New York. 1983.

INTRODUCTION

7

Table 1.4 Highway Runoff Constituents and Their Primary Sources Constituents Particulates Nitrogen, phosphorus Lead Zinc Iron Copper Cadmium Chromium Nickel Manganese Cyanide Sodium, calcium, chloride Sulfate Petroleum PCB

Primary Sources Pavement wear, vehicles, atmosphere, maintenance Atmosphere, roadside fertilizer application Leaded gasoline (auto exhaust), tire wear (lead oxide filler material, lubricating oil and grease, bearing wear) Tire wear (filler materials), motor oil (stabilizing additive), grease Auto body rust, steel highway structures (guard rails, etc.), moving engine parts Metal plating, bearing and bushing wear, moving engine parts, brake lining wear, fungicides and insecticides Tire wear (filler material), insecticide application Metal plating, moving engine parts, break lining wear Diesel fuel and gasoline (exhaust), lubricating oil, metal plating, bushing wear, brake lining wear, asphalt paving Moving engine parts Anticake compound (ferric ferrocyanide, sodium ferrocyanide, yellow prussiate of soda) used to keep deicing salt granular Deicing salts Roadway beds, fuel, deicing salts Spills, leaks, or blow-by of motor lubricants, antifreeze and hydraulic fluids, asphalt surface leachate Spraying of highway rights-of-way, background atmospheric deposition, PCB catalyst in synthetic tires

From U.S. DOT, FHWA, Report No. FHWA/RD-84/056-060, June 1987.

and fluoranthene (23% of the samples). These 13 compounds were similar to those reported in most areas. The most common organic toxicants have been from automobile usage (polycyclic aromatic hydrocarbons, or PAHs), combustion of wood and coal (PAHs), industrial and home use solvents (halogenated aliphatics and other volatiles), wood preservatives (PAHs, creosote, pen­ tachlorophenol), and a variety of agricultural, municipal, and highway compounds, and pesticides. The major urban pollution sources are construction sites, on-site sewage disposal systems, households, roadways, golf courses, parks, service stations, and parking areas (Pitt et al. 1995). The primary pollutant from construction is eroded soils (suspended and bedload sediments, dis­ solved solids, turbidity), followed by hydrocarbons, metals, and fertilizers. Silviculture is a major source of nonpoint pollution in many areas of the country. The primary pollutant is eroded soils, which result in elevated turbidity, silted substrates, altered habitat, higher dissolved solids, and altered ion ratios in the streams and lakes of the watershed. Water temperatures increase as tree canopies are removed and stream flow slows. Fertilizers and pesticides may also be used which are transported to the streams via surface runoff, groundwater, and drift. Agricultural activities contribute a wide variety of stormwater pollutants, depending on the production focus and ecoregion. Major pollutants include eroded soils, fertilizers, pesticides, hydrocarbons (equipment-related), animal wastes, and soil salts. The hydromodification category of NPS includes dredging, channelization, bank stabilization, and impoundments. Stormwaters obviously do not “run off” any of these sources, but stormwater (high flow) does degrade waters associated with these sources. Water quality parameters which may be affected by these sources during stormwater events include turbidity, sediment loading (habitat alteration), dissolved solids, temperature, nutrients, metals, synthetic organics, dissolved oxygen, pathogens, and toxicity. Of a more site-specific nature, resource extraction, land waste disposal, and contaminated sediments are sources of pollutants during stormwater events. Activities such as sand and gravel, metal, coal, and oil and gas extraction from or near receiving waters may contribute to habitat alteration and increased turbidity, siltation, metals, hydrocarbons, and salt during storm events. Land waste disposal sources consist of sludge farm runoff, landfill and lagoon runoff and leachate, and on-site septic system (leachfield) overflows. These sources may contribute a variety of pollutants

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STORMWATER EFFECTS HANDBOOK

to receiving waters such as nutrients, solids (dissolved and suspended), pathogens, metals, and synthetic organics. Contaminated sediments occur in numerous areas throughout the United States (EPA 1994). Many nutrients and toxic metals, metalloids, and synthetic organics readily sorb to particulates (organic or inorganic) which accumulate as bedded sediments. During storm events, these sediments may be resuspended and then become more biologically active by pollutant desorption, transformation, or particle uptake by organism ingestion. The specific stormwater pollutants vary dramatically in their fate and effect characteristics. In most assessments of NPS pollution, there are many unknowns, such as: • What are the pollutants of concern? • What are the pollutant sources? • What are the pollutant loadings?

These common unknowns provide the rationale for use of an integrated assessment strategy (see Unit 2) which incorporates several essential components of runoff-receiving water systems.

REGULATORY PROGRAM In February 1987, amendments to the federal Clean Water Act (CWA) were passed by Congress and required states (Sections 101 and 319) to assess NPS pollution and develop management programs. These programs are to be tailored on a watershed-specific basis, although they are structured along political jurisdictions. There are also NPS requirements under Section 6217 of the Coastal Zone Act Reauthorization Amendments of 1990. The EPA published the Phase 1 stormwater discharge regulations for the CWA in the Federal Register on November 16, 1990. The regulations confirm stormwater as a point source that must be regulated through permits issued under the National Pollutant Discharge Elimination System (NPDES). Certain specified industrial facilities and large municipalities (>100,000 population) fell under the Phase 1 regulations. The Phase 2 regulations were enacted in October 1999, requiring municipalities of 10,000 and greater to comply with stormwater control guidelines. Monitoring activities must be part of the Phase 1 NPDES stormwater permit requirements. One monitoring element is a field screening program to investigate inappropriate discharges to the storm drainage system (Pitt et al. 1993). The Phase 1 requirements also specified outfall monitoring during wet weather to characterize discharges from different land uses. Specified industries are also required to periodically monitor their stormwater discharges. Much of the local municipal effort associated with the Phase 1 permit requirements involved describing the drainage areas and outfalls. Large construction sites are also supposed to be controlled, but enforcement has been very spotty. Local governments have been encouraged by the EPA to develop local stormwater utilities to pay for the review and enforcement activities required by this regulation. The Phase 2 permit require­ ments are likely to have reduced required monitoring efforts for small communities and remaining industries. The Stormwater Phase 2 Rule was published in early November 1999 in the Federal Register. The purpose of the rule is to designate additional sources of stormwater that need to be regulated to protect water quality. Two new classes of facilities are designated for automatic coverage on a nationwide basis: 1. Small municipal separate storm sewer systems located in urbanized areas (about 3500 municipal­ ities) [Phase 1 included medium and large municipalities, having populations greater than 100,000] 2. Construction activities that disturb between 1 and 5 acres of land (about 110,000 sites a year) [Phase 1 included construction sites larger than 5 acres]

INTRODUCTION

9

There is also a new “no exposure” incentive for Phase 1 sites having industrial activities. It is expected that this will exclude about 70,000 facilities nationwide from the stormwater regulations. The NPDES permitting authority would need to issue permits (most likely general permits) by May 31, 2002. Proposed construction site regulations in the Phase 2 rule include: 1. Ensure control of other wastes at construction sites (discarded building materials, concrete truck washout, sanitary wastes, etc.) 2. Implement appropriate best management practices (such as silt fences, temporary detention ponds, etc.) 3. Require preconstruction reviews of site management plans 4. Receive and consider public information 5. Require regular inspections during construction 6. Have penalties to ensure compliance

If local regulations incorporate the following principles and elements into the stormwater program, they would be considered as “qualifying” programs that meet the federal requirements: Five Principles 1. Good site planning 2. Minimize soil movement 3. Capture sediment 4. Good housekeeping practices 5. Mitigation of post-construction stormwater discharges Eight Elements 1. Program description 2. Coordination mechanism 3. Requirements for nonstructural and structural BMPs 4. Priorities for site inspections 5. Education and training 6. Exemption of some activities due to limited impacts 7. Incentives, awards, and streamlining mechanisms 8. Description of staff and resources

Unfortunately, many common stormwater parameters which cause acute and chronic toxicity or habitat problems are not included in typical monitoring programs conducted under the NPDES stormwater permit program. Therefore, stormwater discharges that are degrading receiving waters may not be identified as significant outfalls from these monitoring efforts. Conversely, these data may suggest significant pollution is adversely affecting receiving waters, when in fact it is not. As discussed later in this book, the recent promotion and adoption of integrated assessment approaches which utilize stream biological community indices, toxicity, and habitat characterization of receiv­ ing waters provide much more reliable data on stormwater discharge effects and water quality. Section 304 of the CWA directs EPA to develop and publish information on methods for measuring water quality and establishing water quality criteria for toxic pollutants. These other approaches include biological monitoring and assessment methods which assess the effects of pollutants on aquatic communities and factors necessary to restore and maintain the chemical, physical, and biological integrity of all waters. These “toolboxes” are intended to enable local users to make more efficient use of their limited monitoring resources. Of course, a primary purpose of this book is also to provide guidance to this user community. As such, it is hoped that this book can be considered a “super” toolbox, especially with its large number of references for additional information and its detailed case studies.

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STORMWATER EFFECTS HANDBOOK

APPLICATIONS OF THE HANDBOOK The first aspect of designing a monitoring program is describing how the data are to be used. This may include future uses of the data and must also include the necessary quality of the data (allowable errors). Many uses of the data may be envisioned, as shown in the following brief discussion. Data may be used in the evaluation of local stormwater problems (risk assessments) and identification of pollutant sources to support a comprehensive stormwater management program, compliance monitoring required by regulations, model calibration and verification for TMDL (total maximum daily load) evaluations, evaluation of the performance of control practices, screen­ ing analyses to identify sources of pollutants, etc. It is critical that an integrated assessment approach (designed on a site-specific basis) be used to improve the validity of the assessment and its resulting conclusions. Critical aspects of this are discussed below. Stormwater Management Planning (Local Problem Evaluations and Source Identifications) Stormwater management planning encompasses a wide range of site-specific issues. The local issues that affect stormwater management decisions include understanding local problems and the sources of pollutants or flows that affect these problems. Local monitoring therefore plays an important role in identifying local problems and sources. The main purpose of treating stormwater is to reduce its adverse impacts on receiving water beneficial uses. Therefore, it is important in any stormwater runoff study to assess the detrimental effects that runoff is actually having on a receiving water. Receiving waters may have many beneficial use goals, including: • • • • •

Stormwater conveyance (flood prevention) Biological uses (warm water fishery, biological integrity, etc.) Noncontact recreation (linear parks, aesthetics, boating, etc.) Contact recreation (swimming) Water supply

As discussed in Chapter 2, it is unlikely that any of these uses can be fully obtained with full development in a watershed and with no stormwater controls. However, the magnitude of these effects varies greatly for different conditions. Obviously, local monitoring and evaluation of data are needed to describe specific local problems, especially through the use of an integrated moni­ toring approach that considers physical, chemical, and biological observations collectively. As described throughout this book, relying only on a single aspect of receiving water conditions, or applying general criteria to local data, can be very misleading, and ultimately expensive and ineffective. After local receiving problems are identified, it is necessary to understand what is causing the problems. Again, this can be most effectively determined through local monitoring. Runoff is comprised of many separate source area flow components and phases that are discharged through the storm drainage system and includes warm weather stormwater, snowmelt, baseflows, and inappropriate discharges to the storm drainage (“dry-weather” flows). It may be important to consider all of these potential urban flow discharges when evaluating alternative stormwater man­ agement options. It may be adequate to consider the combined outfall conditions alone when evaluating the longterm, area-wide effects of many separate outfall discharges to a receiving water. However, if better predictions of outfall characteristics (or the effects of source area controls) are needed, then the separate source area components must be characterized. The discharge at an outfall is made up of a mixture of contributions from different source areas. The “mix” depends on the characteristics

INTRODUCTION

11

of the drainage area and the specific rain event. The effectiveness of source area controls is therefore highly site and storm specific. Risk Assessments Risk assessments contain four major components (NRC 1983): • • • •

Hazard identification Effects characterization Exposure characterization Risk characterization

Hazard identification includes quantifying pollutant discharges, plus modeling the fate of the discharged contaminants. Obviously, substantial site-specific data are needed to prepare the selected model for this important aspect of a risk assessment. Knowledge about the mass and concentration discharges of a contaminant is needed so the transport and fate evaluations of the contaminant can be quantified. Knowledge of the variations of these discharges with time and flow conditions is needed to determine the critical dose–response characteristics for the contaminants of concern. A suitable model, supported by adequate data, is necessary to produce the likely dose–stressor response characteristics. Exposure assessment is related to knowledge of the users of receiving waters and contaminated components (such as contaminated fish that are eaten, contaminated drinking water being consumed, children exposed to contaminated swimming by playing in urban creeks, etc.). Finally, the risk is quantified based on this information, including the effects of all of the possible exposure pathways. Obviously, many types of receiving water and discharge data are needed to make an appropriate risk assessment associated with exposure to stormwater, espe­ cially related to discharge characteristics, fate of contaminants, and verification of contaminated components. The use of calibrated and validated discharge and fate models is therefore necessary when conducting risk assessments. Total Maximum Daily Load (TMDL) Evaluations The total maximum daily load (TMDL) for a stream is the estimated maximum discharge that can enter a water body without affecting its designated uses. TMDLs can be used to allocate discharges from multiple sources and to define the level of control that may be needed. Historically, assimilative capacities of many receiving waters were based on expected dissolved oxygen con­ ditions using in-stream models. Point source discharges of BOD were then allocated based on the predicted assimilative capacity. Allowed discharges of toxic pollutants can be determined in a similar manner. Existing background toxicant concentrations are compared to water quality criteria under critical conditions. The margin in the pollutant concentration (difference between the existing and critical concentrations) is multiplied by the stream flow to estimate the maximum allowable increased discharge, before the critical criteria would likely be exceeded. There has always been concern about margins of safety and other pollutant sources in the simple application of assimilative capacity analyses. The TMDL process is a more comprehensive approach that attempts to examine and consider all likely pollutant sources in the watershed. The EPA periodically publishes guidance manuals describing resources available for conducting TMDL analyses (Shoemaker et al. 1997, for example). Model Calibration and Validation A typical use of stormwater monitoring data is to calibrate and validate models that can be used to examine many questions associated with urbanization, especially related to the design of

12

STORMWATER EFFECTS HANDBOOK

control programs to reduce problem discharges effectively. All models need to be calibrated for local conditions. Local rain patterns and development characteristics, for example, all affect runoff characteristics. Calibration usually involves the collection of an initial set of data that is used to modify the model for these local characteristics. Validation is an independent check to ensure that the calibrated model produces predictions within an acceptable error range. Unfortunately, many models are used to predict future conditions that are not well represented in available data sets, or the likely future conditions are not available in areas that could be monitored. These problems, plus many other aspects of modeling, require someone with good skill and support to ensure successful model use. Model calibration and validation involves several steps that are similar for most stormwater modeling processes. The best scenario may be to collect all calibration information from one watershed and then validate the calibrated model using independent observations from another watershed. Another common approach is to collect calibration information for a series of events from one watershed, and then validate the calibrated model using additional data from other storms from the same watershed. Numerous individual rainfall-runoff events may need to be sampled to cover the range of conditions of interest. For most stormwater models, detailed watershed infor­ mation is also needed. Jewell et al. (1978) presented one of the first papers describing the problems and approaches needed for calibrating and validating nonpoint source watershed scale models. Most models have descriptions of recommended calibration and validation procedures. Models that have been used for many years (such as SWMM and HSPF) also have many publications available describing the sensitivity of model components and the need for adequate calibration. It is very important that adequate QA/QC procedures be used to ensure the accuracy and suitability of the data. Common problems during the most important rainfall-runoff monitoring activities are associated with unrepresentative rainfall data (using too few rain gauges and locating them incorrectly in the watershed), incorrect rain gauge calibrations, poor flow-monitoring condi­ tions (surcharged flows, relying on Manning’s equation for V and Q, poor conditions at the monitoring location), etc. The use of a calibrated flume is preferred, for example. Other common errors are associated with inaccurate descriptions of the watershed (incorrect area, amount of impervious area, understanding of drainage efficiency, soil characteristics, etc.). Few people appre­ ciate the inherent errors associated with measuring rainfall and runoff. Most monitoring programs are probably no more than ±25% accurate for each event. It is very demanding to obtain rainfall and runoff data that is only 10% in error. This is most evident when highly paved areas (such as shopping centers or strip commercial areas) are monitored and the volumetric runoff coefficients are examined. For these areas, it is not uncommon for many of the events to have volumetric runoff coefficient (Rv) values greater than 1.0 (implying more runoff than rainfall). Similar errors occur with other sites but are not as obvious. Data from several watersheds are available for the calibration and validation process. If so, start with data from the simplest area (mostly directly connected paved areas and roofs, with little unpaved areas). This area probably represents commercial roofs and parking/storage areas alone. These areas should be calibrated first, before moving on to more complex areas. The most complex areas, such as typical residential areas having large expanses of landscaped areas and with most of the roofs being disconnected from the drainage areas, should be examined last. Effectiveness of Control Programs Effective stormwater management programs include a wide variety of control options that can be utilized to reduce receiving water problems. With time and experience, some of these will be found to be more effective than others. In order to identify which controls are most cost-effective for a specific area, local performance evaluations should be conducted. In many cases, straightfor­ ward effectiveness monitoring (comparing influent with effluent concentrations for a stormwater filter, for example) can be utilized, while other program elements (such as public education or street

INTRODUCTION

13

cleaning) can be much more difficult to evaluate. Therefore, this book presents monitoring approaches that can be utilized for a broad range of control programs. These monitoring activities may appear to be expensive. However, the true cost of not knowing how well currently utilized controls function under local conditions can be much more costly than obtaining accurate local data and making appropriate changes in design methods. The first concern when investigating alternative treatment methods is determining the needed level of stormwater control. This determination has a great effect on the cost of the stormwater management program and needs to be made carefully. Problems that need to be addressed range from sewerage maintenance issues to protecting many receiving water uses. As an example, Laplace et al. (1992) recommends that all particles greater than about 1 to 2 mm in diameter be removed from stormwater in order to prevent deposition in sewerage. The specific value is dependent on the energy gradient of the flowing water in the drainage system and the hydraulic radius of the sewerage. This treatment objective can be easily achieved using a number of cost-effective source area and inlet treatment practices. In contrast, much greater levels of stormwater control are likely needed to prevent excessive receiving water degradation. Typical treatment goals usually specify about 80% reductions in suspended solids concentrations. For most stormwaters, this would require the removal of most particulates greater than about 10 µm in diameter, about 1% of the 1 mm size noted above to prevent sewerage deposition problems. Obviously, the selection of a treatment goal must be done with great care. There are many stormwater control practices, but not all are suitable in every situation. It is important to understand which controls are suitable for the site conditions and can also achieve the required goals. This will assist in the realistic evaluation for each practice of the technical feasibility, implementation costs, and long-term maintenance requirements and costs. It is also important to appreciate that the reliability and performance of many of these controls have not been well established, with most still in the development stage. This is not to say that emerging controls cannot be effective; however, there is not a large amount of historical data on which to base designs or to provide confidence that performance criteria will be met under the local conditions. Local monitoring can be used to identify the most effective controls based on the sources of the identified problem pollutants, and monitoring can be utilized to measure how well in-place controls are functioning over the long term. These important data can be used to modify recommendations for the use of specific controls, design approaches, and sizing requirements. Compliance with Standards and Regulations The receiving water (and associated) monitoring tools described in this book can also be used to measure compliance with standards and regulations. Numerous state and local agencies have established regulatory programs for moderate and large-sized communities due to the EPA’s NPDES (National Pollutant Discharge Elimination System) stormwater permit program. The recently enacted Phase 2 regulations will extend some stormwater regulations to small communities throughout the United States. In addition, the increasing interest in TMDL evaluations in critical watersheds also emphasizes the need for local receiving water and discharge information. These regulatory programs all require certain monitoring, modeling, and evaluation efforts that can be conducted using procedures and methods described in this book.

REFERENCES Callahan, M.A., M.W. Slimak, N.W. Gabel, I.P. May, C.F. Fowler, J.R. Freed, P. Jennings, R.L. Durfee, F.C. Whitmore, B. Maestri, W.R. Mabey, B.R. Holt, and C. Gould, Water Related Environmental Fates of 129 Priority Pollutants. U.S. Environmental Protection Agency, Monitoring and Data Support Divi­ sion, EPA-4-79-029a and b. Washington D.C. 1979.

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STORMWATER EFFECTS HANDBOOK

EPA. Results of the Nationwide Urban Runoff Program. Water Planning Division, PB 84-185552, Washington, D.C. December 1983. EPA. Procedures for Assessing the Toxicity and Bioaccumulation of Sediment-Associated Contaminants with Freshwater Invertebrates, EPA 600/R-94/024, U.S. Environmental Protection Agency, Duluth, MN. 1994. Jewell, T.K., T.J. Nunno, and D.D. Adrian. Methodology for calibrating stormwater models. J. Environ. Eng. Div. 104: 485. 1978. Laplace, D., A. Bachoc, Y. Sanchez, and D. Dartus. Truck sewer clogging development — description and solutions. Water Sci. Technol. 25(8): 91–100. 1992. May, C.W. Assessment of the Cumulative Effects of Urbanization on Small Streams in the Puget Sound Lowland Ecoregion: Implications for Salmonid Resource Management. Ph.D. dissertation, University of Wash­ ington, Seattle. 1996. NRC (National Research Council). Risk Assessment in the Federal Government: Managing the Process. National Academy Press. Washington, D.C. 1983. ODNR (Ohio Department of Natural Resources). Ohio Nonpoint Source Management Program. Ohio Depart­ ment of Natural Resources, Columbus, OH. 1989. Pitt, R.E., R.I. Field, M.M. Lalor, D.D. Adrian, D. Barbé, Investigation of Inappropriate Pollutant Entries into Storm Drainage Systems: A User's Guide. Rep. No. EPA/600/R-92/238, NTIS Rep. No. PB93131472/AS, U.S. EPA, Storm and Combined Sewer Pollution Control Program, Edison, NJ. Risk Reduction Engineering Lab., Cincinnati, OH. 1993. Pitt, R., R. Field, M. Lalor, and M. Brown. Urban stormwater toxic pollutants: assessment, sources and treatability. Water Environ. Res. 67(3): 260–275. May/June 1995. Shoemaker, L., M. Lahlou, M. Bryer, D. Kumar, and K. Kratt. Compendium of Tools for Watershed Assessment and TMDL Development. EPA 841-B-97-006. U.S. Environmental Protection Agency. Office of Water. Washington, D.C. May 1997. U.S. Department of Transportation (DOT). FHWA/RD-84/056-060, June 1987. Verschueren, K. Handbook of Environmental Data on Organic Chemicals, 2nd edition. Van Nostrand Reinhold, New York. 1983.

CHAPTER

2

Receiving Water Uses, Impairments, and Sources of Stormwater Pollutants “Bathing in sewage-polluted seawater carries only a negligible risk to health, even on beaches that are aesthetically very unsatisfactory.” Committee on Bathing Beach Contamination Public Health Laboratory Service of the U.K. 1959

CONTENTS Introduction ......................................................................................................................................15 Beneficial Use Impairments.............................................................................................................22 Recognized Value of Human-Dominated Waterways............................................................22 Stormwater Conveyance (Flood Prevention) .........................................................................26 Recreation (Non-Water Contact) Uses...................................................................................26 Biological Uses (Warm-Water Fishery, Aquatic Life Use, Biological Integrity, etc.)..........27 Human Health-Related Uses (Swimming, Fishing, and Water Supply) ...............................28 Likely Causes of Receiving Water Use Impairments .....................................................................30 Major Urban Runoff Sources ..........................................................................................................31 Construction Site Erosion Characterization...........................................................................32 Urban Runoff Contaminants ..................................................................................................34 Summary ..........................................................................................................................................42 References ........................................................................................................................................43

INTRODUCTION Wet-weather flow impacts on receiving waters have been historically misunderstood and deemphasized, especially in times and areas of poorly treated municipal and industrial discharges. The above 1959 quote from the Committee on Bathing Beach Contamination of the Public Health Laboratory Service of the U.K. demonstrates the assumption that periodic combined sewer overflows (CSOs), or even raw sewage discharges, produced negligible human health risks. Is it any wonder then that the much less dramatically contaminated stormwater discharges have commonly been considered “clear” water by many regulators? The EPA reported that only 57% of the rivers and streams in the United States fully support their beneficial uses (Figure 2.1). A wide variety of pollutants and sources are the cause of impaired 15

16

STORMWATER EFFECTS HANDBOOK

Overall Use Support in Surveyed Rivers and Streams

Good (Fully Supporting) 57%

Fair Poor (Partially Good (Not (Threatened) Supporting) Supporting) 22% 7% 14%

Figure 2.1 U.S. rivers and streams meet­ ing designated beneficial uses. Note: Per­ centages do not add to 100% because more than one pollutant or source may impair a segment of ocean shoreline. (From U.S. Environmental Protection Agency. National Water Quality Inventory. 1994 Report to Congress. Office of Water. EPA 841-R-95005. Washington, D.C. December 1995.)

Poor (Not Attainable) 50% of surface of the substrates is embedded in fine material. Embedded substrates cannot be easily dislodged. This also includes substrates that are concreted or “armor-plated.” Naturally sandy streams are not considered embedded; however, a sand-predominated stream that is the result of anthropogenic activities that have buried the natural coarse substrates is considered embedded. Boxes are checked for extensiveness (area of sampling zone) of the embedded substrates as follows: Extensive: >75% of site area, Moderate: 50 to 75%, Sparse: 25 to 50%, Low: 20, the maximum score allowed for the QHEI is limited to 20 points. Metric 2: In-Stream Cover This metric consists of in-stream cover type and in-stream cover amount. All of the cover types that are present in amounts greater than approximately 5% of the sampling area (i.e., they occur in sufficient quantity to support species that may commonly be associated with the habitat type) should be checked. Cover should not be counted when it is in areas of the stream with insufficient depth (usually 70 cm), (6) oxbows, (7) boulders, (8) aquatic macrophytes, and (9) rootwads (tree roots that extend into stream). Do not check undercut banks AND rootwads unless undercut banks exist along with rootwads as a major component. Cover Metric Score — Although the theoretical maximum score is >20, the maximum score assigned for the QHEI for the in-stream cover metric is limited to 20 points.

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Metric 3: Channel Morphology This metric emphasizes the quality of the stream channel that relates to the creation and stability of macrohabitat. It includes channel sinuosity (i.e., the degree to which the stream meanders), channel development, channelization, and channel stability. One box under each should be checked unless conditions are considered to be intermediate between two categories; in these cases check two boxes and average their scores. a. Sinuosity — No sinuosity is a straight channel. Low sinuosity is a channel with only one or two poorly defined outside bends in a sampling reach, or perhaps slight meandering within modified banks. Moderate sinuosity is more than two outside bends, with at least one bend well defined. High sinuosity is more than two or three well-defined outside bends with deep areas outside and shallow areas inside. Sinuosity may be more conceptually described by the ratio of the stream distance between these same two points, taken from a topographic map. Check only one box. b. Development — This refers to the development of riffle/pool complexes. Poor means riffles are absent, or if present, shallow with sand and fine gravel substrates; pools, if present, are shallow. Glide habitats, if predominant, receive a Poor rating. Fair means riffles are poorly developed or absent; however, pools are more developed with greater variation in depth. Good means better defined riffles present with larger substrates (gravel, rubble, or boulder); pools vary in depth and there is a distinct transition between pools and riffles. Excellent means development is similar to the Good category except the following characteristics must be present: pools must have a maximum depth of >1 m and deep riffles and runs (>0.5 m) must also be present. In streams sampled with wading methods, a sequence of riffles, runs, and pools must occur more than once in a sampling zone. Check one box. c. Channelization — This refers to anthropogenic channel modifications. Recovered refers to streams that have been channelized in the past, but which have recovered most of their natural channel characteristics. Recovering refers to channelized streams which are still in the process of regaining their former, natural characteristics; however, these habitats are still degraded. This category also applies to those streams, especially in the Huron/Erie Lake Plain ecoregion (NW Ohio), that were channelized long ago and have a riparian border of mature trees, but still have Poor channel characteristics. Recent or No Recovery refers to streams that were recently channelized or those that show no significant recovery of habitats (e.g., drainage ditches, grass lined or rock riprap banks, etc.). The specific type of habitat modification is also checked in the two columns, but not scored. d. Stability — This refers to channel stability. Artificially stable (concrete) stream channels receive a High score. Even though they are generally a negative influence on fish, the negative effects are related to features other than their stability. Channels with Low stability are usually characterized by fine substrates in riffles that often change location, have unstable and severely eroding banks, and a high bedload that slowly creeps downstream. Channels with Moderate stability are those that appear to maintain stable riffle/pool and channel characteristics, but which exhibit some symptoms of instability, e.g., high bedload, eroding or false banks, or show the effects of wide fluctuations in water level. Channels with High stability have stable banks and substrates, and little or no erosion and bedload. e. Modifications/Other — Check the appropriate box if impounded, islands present, or leveed (these are not included in the QHEI scoring) as well as the appropriate source of habitat modifications.

The maximum QHEI metric score for Channel Morphology is 20 points. Metric 4: Riparian Zone and Bank Erosion This metric emphasizes the quality of the riparian buffer zone and quality of the floodplain vegetation. This includes riparian zone width, floodplain quality, and extent of bank erosion. Each of the three components requires scoring the left and right banks (looking downstream). The average of the left and right banks is taken to derive the component value. One box per bank should be

HABITAT CHARACTERIZATION

649

checked unless conditions are considered to be intermediate between two categories; in these cases check two boxes and average their scores. a. Width of Floodplain Vegetation — This is the width of the riparian (stream side) vegetation. Width estimates are only done for forest, shrub, swamp, and old field vegetation. Old field refers to a fairly mature successional field that has stable, woody plant growth; this generally does not include weedy urban or industrial lots that often still have high runoff potential. Two boxes, one each for the left and right bank (looking downstream), should be checked and then averaged. b. Floodplain Quality — The two most predominant floodplain quality types should be checked, one each for the left and right banks (includes urban, residential, etc.), and then averaged. By floodplain we mean the areas immediately outside the riparian zone or greater than 100 ft from the stream, whichever is wider on each side of the stream. These are areas adjacent to the stream that can have direct runoff and erosional effects during normal wet weather. We do not limit it to the riparian zone, and it is much less encompassing than the stream basin. c. Bank Erosion — The following Streambank Soil Alteration Ratings should be used; check one box for each side of the stream and average the scores. False banks mean banks that are no longer adjacent to the normal flow of the channel but have been moved back into the floodplain, most commonly as a result of livestock trampling. 1. None — stream banks are stable and not being altered by water flows or animals (e.g., livestock) — Score 3. 2. Little — stream banks are stable, but are being lightly altered along the transect line; less than 25% of the stream bank is receiving any kind of stress, and if stress is being received it is very light; less than 25% of the stream bank is false, broken down, or eroding — Score 3. 3. Moderate — stream banks are receiving moderate alteration along the transect line; at least 50% of the stream bank is in a natural stable condition; less than 50% of the stream bank is false, broken down, or eroding; false banks are rated as altered — Score 2. 4. Heavy — stream banks have received major alterations along the transect line; less than 50% of the stream bank is in a stable condition; over 50% of the stream bank is false, broken down, or eroding — Score 1. 5. Severe — stream banks along the transect line are severely altered; less than 25% of the stream bank is in a stable condition; over 75% of the stream bank is false, broken down, or eroding — Score 1.

The maximum score for Riparian Zone and Erosion metric is 10 points. Metric 5: Pool/Glide and Riffle-Run Quality This metric emphasizes the quality of the pool, glide, and/or riffle-run habitats. This includes pool depth, overall diversity of current velocities (in pools and riffles), pool morphology, riffle-run depth, riffle-run substrate, and riffle-run substrate quality. A. POOL/GLIDE QUALITY 1. Maximum depth of pool or glide — check one box only (Score 0 to 6). Pools or glides with maximum depths of less than 20 cm are considered to have lost their function and the total metric is scored a 0. No other characteristics need be scored in this case. 2. Current Types — check each current type that is present in the stream (including riffles and runs; score — 2 to 4), definitions are: Torrential — extremely turbulent and fast flow with large standing waves; water surface is very broken with no definable, connected surface; usually limited to gorges and dam spillway tailwaters. Fast — mostly nonturbulent flow with small standing waves in riffle-run areas; water surface may be partially broken, but there is a visibly connected surface. Moderate — nonturbulent flow that is detectable and visible (i.e., floating objects are readily transported downstream); water surface is visibly connected.

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Slow — water flow is perceptible, but very sluggish. Eddies — small areas of circular current motion usually formed in pools immediately downstream from riffle-run areas. Interstitial — water flow that is perceptible only in the interstitial spaces between substrate par­ ticles in riffle-run areas. Intermittent — no flow is evident anywhere leaving standing pools that are separated by dry areas. 3. Morphology — Check Wide if pools are wider than riffles, Equal if pools and riffles are the same width, and Narrow if the riffles are wider than the pools (Score 0 to 2). If the morphology varies throughout the site, average the types. If the entire stream area (including areas outside of the sampling zone) is pool or riffle, then check riffle = pool.

Although the theoretical maximum score is >12, the maximum score assigned for the QHEI for the Pool Quality metric is limited to 12 points. B. RIFFLE-RUN QUALITY (score 0 for this metric if no riffles are present) 1. Riffle/Run Depth — Select one box that most closely describes the depth characteristics of the riffle (Score 0 to 4). If the riffle is generally less than 5 cm in depth, riffles are considered to have lost their function and the entire riffle metric is scored a 0. 2. Riffle/Run Substrate Stability — Select one box from each that best describes the substrate type and stability of the riffle habitats (Score 0 to 2). 3. Riffle/Run Embeddedness — Embeddedness is the degree that cobble, gravel, and boulder substrates are surrounded or covered by fine material (sand, silt). We consider substrates embedded if >50% of the surface of the substrates is embedded in fine material, as these substrates cannot be easily dislodged. This also includes substrates that are concreted. Boxes are checked for extensiveness (riffle area of sampling zone) with embedded substrates: Exten­ sive: >75% of stream area, Moderate: 50 to 75%, Sparse: 25 to 50%, Low: 30.6 a

Drainage Area (mi2)

> 622.9

Very Low 0–1.0 2 0–1.0 2 0–1.0 2

4 —

Low

Low– Moderate

Moderate

Moderate– High

High

Very Higha

1.1–5.0 4 1.1–3.0 4 1.1–2.5 4 0–1.0

5.1–10.0 6 3.1–6.0 6 2.6–5.0 6 1.1–2.0

10.1–15.0 8 6.1–12.0 10 5.1–7.5 8 2.1–4.0

15.1–20 10 12.1–18.0 10 7.6–12.0 10 4.1–6.0

20.1–30 10 18.0–30 8 12.1–20 8 6.1–10.0

30.1–40 8 30.1–40 6 20.1–30 6 10.1–15

8 0.6–1.0 8

10 1.1–2.5 10

10 2.6–4.0 10

8 4.1–9.0 10

6 > 9.0 8

6 0–0.5 6

Any site with a gradient greater than the upper bound of the “very high” gradient classification is assigned a score of 4.

1. Additional Comments/Pollution Impacts — Different types of pollution sources (e.g., wastewater treatment plant, feedlot, industrial discharge, nonpoint source inputs) are noted with their proximity (in 0.1-mile increments) to the sampling site; any evidence of litter, either in-stream or on the stream bank, is also noted. 2. Sampling Gear/Distance Sampled — The type of fish sampling gear used during each pass is specified, and any variation in sampling procedures is noted (e.g., sampler type A specifies sampling along one shoreline of 0.5 km, but due to local restriction, sampling may be performed on both shorelines to accumulate 0.5 km); the total sampling distance in kilometers for each sampling site for each pass is recorded. 3. Water Clarity — The following descriptions can be used as a guide: a. Clear — bottom is clearly visible (if shallow enough), and the water contains no apparent color or staining. b. Stained — usually a brownish (or other) color to the water; the bottom may be visible in shallow areas. c. Turbid — bottom seldom visible at more than a few inches; caused by suspended sediment particles. The apparent source of stained (e.g., tannic acid, leaf decay, etc.) and turbid (e.g., runoff [clay/silt], algae/diatoms, sewage, etc.) water may be specified under additional comments. 4. Water Stage — This is the general water level of the stream during each pass; suggested descriptors are: a) flood, b) high, c) elevated, d) normal, e) low, and f) interstitial. (Note: sampling should not be conducted during flood or high flows.) 5. Canopy — This is the percentage of the sampling site that is not covered or shaded by woody bank vegetation. In wide streams and rivers, this determination should be made along both sides of the river or stream (i.e., the percent of the sampling path that is open). 6. Gradient — Check the box that best describes the gradient at the site. This will be used to check the accuracy of gradients taken from topographic maps. 7. Field Crew — The names of all individuals involved with the sampling/site description at each site are included. 8. Photographs — The number of each photograph taken is recorded; the subject of the photograph is briefly described. 9. Stream Measurements (optional) — When measuring the individual sampling sites, length, width, and average and maximum depth information should be recorded; each measurement should be recorded as either a riffle, run, or pool or glide by placing an X in the correct box to the right of where measurements are recorded (Figure A.2); see the introduction for definitions of riffles, runs, etc. The number of width measurements is left to the discretion of the field crew leader. Short riffles may require only one or two width measurements, while long pools will probably require more,

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depending on the degree of variation that exists in the stream’s width. Depth measurements should be made in association with individual width measurements. Depths should be taken at the stream margins and various points across the stream. Up to nine depth measurements may be taken, depending on the variability in the stream bottom. Maximum depth is the deepest spot in the stream section sampled. One purpose of this information is to calculate pool volume. 10. Stream Diagram — Cross sections: Two or three cross sections of the stream are drawn to provide information on features of the stream bank, stream bottom, stream channel, and floodplain. Channel — The cross section containing the stream that is distinct from the surrounding area due to breaks in the general slope of the land, lack of terrestrial vegetation, and changes in the com­ position of the substrate materials. The channel is made up of stream banks and stream bottoms. Banks — The portion of the channel cross section that tends to restrict lateral movement of water. The banks often have a slope steeper than 45° and exhibit a distinct break in slope from the stream bottom. Also, an obvious change in substrate materials is a reliable delineation of the bank. Stream Bottom — The portion of the channel cross section not classified as bank. The bottom is usually composed of stream sediments or water transported debris and may be covered by rooted or clinging aquatic vegetation. In some geologic formations, the stream bottom may consist of bedrock rather than sediments. Floodplain — The area adjacent to the channel that is seasonally submerged under water. Usually the floodplain is a low area covered by various types of riparian vegetation.

Stream Map The entire sampling zone is sketched in the area provided. Important physical features are noted on the map with standard symbols used where possible. The sampling path taken is described, along with any other pertinent information.

THE USEPA HABITAT ASSESSMENT FOR THE RAPID BIOASSESSMENT PROTOCOLS (EPA 1999) Rosgen (1985, 1994, 1996) presented a stream and river classification system that is founded on the premise that dynamically stable stream channels have a morphology that provides appropriate distribution of flow energy during storm events. Further, he identifies eight major variables that affect the stability of channel morphology, but are not mutually independent: channel width, channel depth, flow velocity, discharge, channel slope, roughness of channel materials, sediment load, and sediment particle size distribution. When streams have one of these characteristics altered, some of their capability to dissipate energy properly is lost (Leopold et al. 1964; Rosgen 1985) and will result in accelerated rates of channel erosion. Some of the habitat structural components that function to dissipate flow energy are sinuosity, roughness of bed and bank materials, presence of point bars (slope is an important characteristic), vegetative conditions of stream banks and the riparian zone, condition of the floodplain (accessibility from bank, overflow, and size are important characteristics). Measurement of these parameters or characteristics serves to stratify and place streams into distinct classifications. However, none of these habitat classification techniques attempts to differ­ entiate the quality of the habitat and the ability of the habitat to support the optimal biological condition of the region. Much of our understanding of habitat relationships in streams has emerged from comparative studies that describe statistical relationships between habitat variables and abun­ dance of biota (Hawkins et al. 1993). A rapid and qualitative habitat assessment approach has been developed to describe the overall quality of the physical habitat (Ball 1982; Ohio EPA 1987; Plafkin

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et al. 1989; Barbour and Stribling 1991, 1994; Rankin 1991, 1995). For a more detailed guidance, please refer to the original document (USEPA 1999, www.epa.gov/owow/monitoring/rbp/). The habitat assessment matrix developed for the Rapid Bioassessment Protocols (RBPs) in Plafkin et al. (1989) were originally based on the Stream Classification Guidelines for Wisconsin developed by Ball (1982) and “Methods of Evaluating Stream, Riparian, and Biotic Conditions” developed by Platts et al. (1983). Barbour and Stribling (1991, 1994) modified the habitat assess­ ment approach originally developed for the RBPs to include additional assessment parameters for high-gradient streams and a more appropriate parameter set for low-gradient streams. All parameters are evaluated and rated on a numerical scale of 0 to 20 (highest) for each sampling reach. The ratings are then totaled and compared to a reference condition to provide a final habitat ranking. Scores increase as habitat quality increases. To ensure consistency in the evaluation procedure, descriptions of the physical parameters and relative criteria are included in the rating form (Figures A.3 through A.8). A biologist who is well versed in the ecology and zoogeography of the region can generally recognize optimal habitat structure as it relates to the biological community. The ability to accurately assess the quality of the physical habitat structure using a visual-based approach depends on several factors: the parameters selected to represent the various features of habitat structure need to be relevant and clearly defined; a continuum of conditions for each parameter must exist that can be characterized from the optimum for the region or stream type under study to the poorest situation reflecting substantial alteration due to anthropogenic activities; the judgment criteria for the attributes of each parameter should minimize subjectivity through either quantitative measurements or specific categor­ ical choices, in which the investigators are experienced or adequately trained, for stream assessments in the region under study (Hannaford et al. 1997); adequate documentation and ongoing training must be maintained to evaluate and correct errors resulting in outliers and aberrant assessments. Habitat evaluations are first made on in-stream habitat, followed by channel morphology, bank structural features, and riparian vegetation. Generally, a single, comprehensive assessment is made that incorporates features of the entire sampling reach as well as selected features of the catchment. Additional assessments may be made on neighboring reaches to provide a broader evaluation of habitat quality for the stream ecosystem. The actual habitat assessment process involves rating the 10 parameters as optimal, suboptimal, marginal, or poor, based on the criteria included on the Habitat Assessment Field Data Sheets. Some state programs, such as Florida Department of Environmental Protection (DEP) (1996) and Mid-Atlantic Coastal Streams Workgroup (MACS) (1996) have adapted this approach using somewhat fewer and different parameters. Reference conditions are used to scale the assessment to the “best attainable” situation. This approach is critical to the assessment because stream characteristics will vary dramatically across different regions (Barbour and Stribling 1991). The ratio between the score for the test station and the score for the reference condition provides a percent comparability measure for each station. The station of interest is then classified on the basis of its similarity to expected conditions (reference condition), and its apparent potential to support an acceptable level of biological health. Use of a percent comparability evaluation allows for regional and stream-size differences which affect flow or velocity, substrate, and channel morphology. Some regions are characterized by streams having a low channel gradient, such as coastal plains or prairie regions. Other habitat assessment approaches or a more rigorously quantitative approach to measuring the habitat parameters may be used (see Klemm and Lazorchak 1994; Kaufmann and Robison 1994; Meador et al. 1993). However, holistic and rapid assessment of a wide variety of habitat attributes along with other types of data is critical if physical measurements are to be used to best advantage in interpreting biological data. A generic habitat assessment approach based on visual observation can be separated into two basic approaches — one designed for high-gradient streams, and one designed for low-gradient streams. High-gradient or riffle/run prevalent streams are those in moderate- to high-gradient land­ scapes. Natural high-gradient streams have substrates primarily composed of coarse sediment particles

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Figure A.3 For use in Rapid Bioassessment Protocols. (From EPA. Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. EPA 841/B-99/002. 1999.)

(i.e., gravel or larger) or frequent coarse particulate aggregations along stream reaches. Low-gradient or glide/pool prevalent streams are those in low- to moderate-gradient landscapes. Natural low-gradient streams have substrates of fine sediment or infrequent aggregations of more coarse (gravel or larger) sediment particles along stream reaches. The entire sampling reach is evaluated for each parameter. A brief set of decision criteria is given for each parameter corresponding to each of the four categories, reflecting a continuum of conditions on the field sheet (optimal, suboptimal, marginal, and poor).

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Figure A.4 For use in Rapid Bioassessment Protocols. (From EPA. Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. EPA 841/B-99/002. 1999.)

Use of a percent comparability evaluation allows for regional and stream-size differences that affect flow or velocity, substrate, and channel morphology. Some regions are characterized by streams having a low channel gradient. Such streams are typically shallower, have a greater pool/riffle or run/bend ratio, and have a less stable substrate than streams with a steep channel gradient. Although some low-gradient streams do not provide the diversity of habitat or fauna afforded by steeper-

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Figure A.5 For use with Rapid Bioassessment Protocols. (From EPA. Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. EPA 841/B-99/002. 1999.)

gradient streams, they are characteristic of certain regions. Using the approach presented here, these streams may be evaluated relative to other low-gradient streams (USEPA 1989). Assessment Category Comparable to reference Supporting Partially supporting Nonsupporting

Percent of Comparability ≥90% 75–88% 60–73% ≤58%

Water Quality Information requested in this section is standard to many aquatic studies and allows for some comparison between sites. Additionally, conditions that may significantly affect aquatic biota are

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Figure A.6 For use with Rapid Bioassessment Protocols. (From EPA. Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. EPA 841/B-99/002. 1999.)

documented. Documentation of recent and current weather conditions is important because of the potential impact that weather may have on water quality. To complete this phase of the bioassessment, a photograph may be helpful in identifying station location and documenting habitat conditions. Any observations or data not requested but deemed important by the field observer should be recorded. This section is identical for all protocols, and the specific data requested are described below: Temperature (C), Dissolved Oxygen, pH, Conductivity — Measure and record values for each of the water quality parameters indicated, using the appropriate calibrated water quality instrument(s). Note the type of instrument and unit number used.

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Figure A.7 For use with Rapid Bioassessment Protocols. (From EPA. Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. EPA 841/B-99/002. 1999.)

Stream Type — Note the appropriate stream designation according to state water quality standards. Water Odors — Note those odors described (or include any other odors not listed) that are associated with the water in the sampling area. Water Surface Oils — Note the term that best describes the relative amount of any oils present on the water surface. Turbidity — Note the term which, based upon visual observation, best describes the amount of material suspended in the water column.

Physical Characterization Physical characterization parameters include estimations of general land use and physical stream characteristics such as width, depth, flow, and substrate. The evaluation begins with the riparian zone (stream bank and drainage area) and proceeds in-stream to sediment/substrate descriptions. Such information will provide insight as to what organisms may be present or are expected to be

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Figure A.8 For use with Rapid Bioassessment Protocols. (From EPA. Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. EPA 841/B-99/002. 1999.)

present, and to presence of stream impacts. The information requested in the Physical Character­ ization section of the Field Data Sheet is briefly discussed below: Predominant Surrounding Land Use — Observe the prevalent land-use type in the vicinity (noting any other land uses in the area which, although not predominant, may potentially affect water quality). Local Watershed Erosion — The existing or potential detachment of soil within the local watershed (the portion of the watershed that drains directly into the stream) and its movement into a stream are noted. Erosion can be rated through visual observation of watershed and stream characteristics. (Note any turbidity observed during water quality assessment below.)

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Local Watershed Nonpoint Source Pollution — This item refers to problems and potential problems other than siltation. Nonpoint source pollution is defined as diffuse agricultural and urban runoff. Other compromising factors in a watershed that may affect water quality are feedlots, wetlands, septic systems, dams and impoundments, and/or mine seepage. Estimated Stream Width (m) — Estimate the distance from shore to shore at a transect representative of the stream width in the area. Estimated Stream Depth (m) — Riffle, run, and pool. Estimate the vertical distance from water surface to stream bottom at a representative depth at each of the three habitat types. High Water Mark (m) — Estimate the vertical distance from the stream bank to the peak overflow level, as indicated by debris hanging in bank or floodplain vegetation, and deposition of silt or soil. In instances where bank overflow is rare, a high water mark may not be evident. Velocity — Record an estimate of stream velocity in a representative run area. Dam Present — Indicate the presence or absence of a dam upstream or downstream of the sampling station. If a dam is present, include specific information relating to alteration of flow. Channelized — Indicate whether or not the area around the sampling station is channelized. Canopy Cover — Note the general proportion of open to shaded area which best describes the amount of cover at the sampling station. Sediment Odors — Disturb sediment and note any odors described (or include any other odors not listed) which are associated with sediment in the area of the sampling station. Sediment Oils — Note the term which best describes the relative amount of sediment oils observed in the sampling area. Sediment Deposits — Note those deposits described (or include any other deposits not listed) which are present in the sampling area. Also indicate whether the undersides of rocks not deeply embedded are black (which generally indicates low dissolved oxygen or anaerobic conditions). Inorganic Substrate Components — Visually estimate the relative proportion of each of the several substrate/particle types listed that are present in the sampling area. Organic Substrate Components — Indicate relative abundance of each of the three substrate types listed.

Listed below is a general explanation of some major habitat parameters to be evaluated. Substrate and In-Stream Cover The in-stream habitat characteristics directly pertinent to the support of aquatic communities consist of substrate type and stability, availability of refugia, and migration/passage potential. Bottom Substrate — This refers to the availability of habitat for support of aquatic organisms. A variety of substrate materials and habitat types is desirable. The presence of rock and gravel in flowing streams is generally considered the most desirable habitat. However, other forms of habitat may provide the niches required for community support. For example, logs, tree roots, submerged or emergent vegetation, undercut banks, etc., will provide excellent habitat for a variety of organisms, particularly fish. Bottom substrate is evaluated and rated by observation. Embeddedness — The degree to which boulders, rubble, or gravel are surrounded by fine sediment indicates suitability of the stream substrate as habitat for benthic macroinvertebrates and for fish spawning and egg incubation. Embeddedness is evaluated by visual observation of the degree to which larger particles are surrounded by sediment. In some western areas of the United States, embeddedness is regarded as the stability of cobble substrate by measuring the depth of burial of large particles (cobble, boulders). Stream Discharge and/or Stream Velocity — Stream discharge relates to the ability of a stream to provide and maintain a stable aquatic environment. Stream discharge (and water quality) is most critical to the support of aquatic communities when the representative low flow is ≤0.15 cms (5 cfs). In these small streams, discharge should be estimated in a straight stretch of run area where banks are parallel and bottom contour is relatively flat. Even where a few stations may have discharges in excess of 0.15 cms, discharge may still be the predominating constraint. Therefore, the evaluation is based on discharge rate rather than velocity.

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In larger streams and rivers (>0.15 cms), velocity, in conjunction with depth, has a more direct influence than the discharge rate on the structure of benthic communities (Osborne and Hendricks 1983) and fish communities (Oswood and Barber 1982). The quality of the aquatic habitat can therefore be evaluated in terms of a velocity and depth relationship. As patterned after Oswood and Barber (1982), four general categories of velocity and depth are optimal for benthic and fish communities: (1) slow (0.3 m/s), shallow (