Discover novel stormwater control measures to make for a greener tomorrow!
The protection of our aquatic resources is growing in importance as the effects of climate change and continued urbanization are felt throughout the world. While most rain that falls onto vegetated spaces infiltrates the soil, rain that falls onto impervious surfaces will not, increasing downstream flooding and erosion and causing impaired water quality. Impervious surfaces such as road infrastructure, rooftops, and parking areas all increase runoff and mobilize many pollutants that have deposited on these surfaces that are then carried into our waterways. Proper management of this stormwater through green infrastructure is essential to address these challenges and reduce the environmental and ecological impacts brought about by this runoff.
This book brings into focus resilient stormwater control measures (SCMs) for the reduction of stormwater flows and associated pollutants that can detrimentally impact our local environmental and ecological systems. These interventions are green infrastructure based, utilizing natural hydrologic and environmental features using soil and vegetation to manage stormwater. These technologies include water harvesting, bioretention and bioinfiltration, vegetated swales and filter strips, permeable pavements, sand filters, green roofs, and stormwater wetlands, among others. The basic science and engineering of these technologies is discussed, including performance information and best maintenance practices.
Green Stormwater Infrastructure readers will also find: - Research-informed resilient SCM design fundamentals - Diagrams developed by the authors to enhance understanding - Case studies to illustrate the points elucidated in the book - End-of-chapter problems with a separate solutions manual
Green Stormwater Infrastructure is an ideal resource for environmental, civil, and biological engineers and environmental scientists in the consulting field. Landscape architects, managers and engineers of watershed districts, and members of federal, state, and local governmental agencies - especially those in the departments of environmental protection and transportation - will find many uses for this guidebook. It will also be of interest to professors, upper-level undergraduates and graduate students in environmental, civil, and biological engineering programs.
Table of Contents
Preface xix
About the Authors xxi
Acknowledgements xxiii
About the Companion Website xxv
1 Introduction to Urban Stormwater and Green Stormwater Infrastructure 1
1.1 Population and Urban Infrastructure 1
1.2 Impacts of Urbanization 2
1.3 The US Regulatory Environment 7
1.4 Urban Stormwater Management 12
1.4.1 Flood Control 12
1.4.2 Peak Flow Control 13
1.4.3 Watershed Approach to Peak Flow 14
1.4.4 Water-Quality Control 14
1.5 Climate Change and Stationarity 15
1.6 Green Stormwater Infrastructure 15
1.7 Stormwater Control Measures 17
1.8 Stormwater Infrastructure and Equity 17
References 18
Problems 19
2 Precipitation: The Stormwater Driver 21
2.1 Introduction 21
2.2 The Urban Hydrologic Cycle 21
2.3 Precipitation 23
2.4 Precipitation Depths 24
2.5 Rainfall Patterns 26
2.6 Inter-event Interval 27
2.7 Extreme Event Precipitation 27
2.8 Introducing the Rainfall-Runoff Relationship 29
2.9 Precipitation and Water Quality 30
2.10 Climate Change 31
References 31
Problems 31
3 Water Quality 33
3.1 Introduction 33
3.2 Designated Water Uses 33
3.3 Water-Quality Parameters and Measures 34
3.4 Temperature 34
3.5 pH 35
3.6 Dissolved Oxygen 35
3.7 Turbidity and Particulate Matter 37
3.8 Biodegradable Organic Matter or “Oxygen Demand” 40
3.9 Nitrogen 41
3.9.1 Nitrate 41
3.9.2 Nitrite 42
3.9.3 Ammonium 42
3.9.4 Organic Nitrogen 43
3.9.5 Nitrogen Measurements 43
3.10 Phosphorus 44
3.11 Heavy Metals 46
3.12 Hydrocarbons and Other Organic Pollutants 46
3.12.1 Hydrocarbons 46
3.12.2 Pesticides and Other Organic Chemicals 47
3.13 Pathogens 48
3.14 Dissolved Solids and Conductivity 49
3.15 Trash 50
References 50
Problems 50
4 Ecosystem Services 53
4.1 What Are Ecosystem Services? 53
4.2 Ecosystem Services and Stormwater Management 56
4.3 Stormwater Wetlands and Ecosystem Services 56
4.4 Regulation Services 56
4.4.1 Water Treatment 56
4.4.2 Hydrologic Regulation 56
4.4.3 Climate Regulation 57
4.4.4 Air Quality Regulation 57
4.5 Habitat Services 58
4.6 Production Services 59
4.7 Information Services 60
4.8 Designing SCMs for Ecosystem Services 61
References 61
Problems 63
5 Stormwater Quality 65
5.1 Introduction 65
5.2 Event Mean Concentrations 66
5.3 Urban Runoff Pollutant Concentrations 68
5.3.1 Particulate Matter and Particle Size Distributions 70
5.3.2 Nitrogen and Nitrogen Speciation 71
5.3.3 Phosphorus and Phosphorus Speciation 72
5.3.4 Heavy Metals Concentrations and Speciation 73
5.3.5 PAH and PCBs 74
5.4 Urban Stormwater Pollutant Sources 74
5.5 Pollutant Buildup and Wash Off 76
5.5.1 Pollutographs 76
5.5.2 First Flush 76
5.6 Annual Pollutant Loads 83
5.7 Sampling and Measurements 84
5.8 A Note about Stormwater Quality 84
References 84
Problems 87
6 Watershed Hydrology 89
6.1 Introduction 89
6.2 Precipitation 90
6.2.1 Design Storms 91
6.2.2 Continuous Simulation 97
6.3 Watershed Hydrology 98
6.3.1 Drainage Area Delineation 98
6.3.2 Interception and Depression Storage 99
6.3.3 The Simple Method 100
6.3.4 NRCS Curve Number Method 101
6.3.5 NRCS “Time of Concentration” 106
6.3.6 NRCS Unit Hydrograph 108
6.3.7 Creating the Storm Hydrograph 112
6.4 Peak Flow Methods 113
6.4.1 The Rational Method 113
6.4.2 The NRCS Unit Hydrograph Method 115
6.5 Watershed and SCM Hydraulics 115
6.5.1 Open Channel Flow 115
6.5.2 Orifices 117
6.5.3 Weirs 118
References 120
Problems 121
7 SCM Hydrologic Unit Processes 127
7.1 Introduction 127
7.2 SCM Soil Physics and Infiltration 128
7.2.1 Soil Texture 129
7.2.2 Soil-Water Interactions 130
7.2.3 Soil Hydraulic Properties 134
7.2.4 Green and Ampt Model 137
7.2.5 Karst Areas 140
7.3 Evapotranspiration 141
7.4 Soil Moisture Accounting 147
7.5 Storage Indication Routing 148
7.6 Computer-Based Stormwater Models 148
References 149
Problems 150
8 Unit Processes for Stormwater Quality Mitigation 153
8.1 Introduction 153
8.2 Reactions, Reactors, and Reactor Engineering 154
8.3 Removal of Particulate Matter 158
8.3.1 Sedimentation 158
8.3.2 Filtration 161
8.4 Removal of Dissolved Pollutants: Adsorption 163
8.4.1 Adsorption Equilibrium Models 164
8.4.2 Batch Adsorption 165
8.4.3 Adsorption Column Dynamics 168
8.4.4 Adsorption of Hydrophobic Organic Compounds 169
8.4.5 Adsorption of Heavy Metals 170
8.4.6 Adsorption of Phosphorus 170
8.4.7 Adsorption of Ammonium 171
8.5 Leaching Processes 171
8.6 Microbiological Processes 171
8.6.1 Microbial/Pathogen Survival 172
8.6.2 Organic Matter Degradation 172
8.6.3 Nitrification 173
8.6.4 Denitrification 174
8.7 Phytobiological Processes 175
8.8 Heat Transfer 176
References 177
Problems 178
9 Stormwater Performance Measures and Metrics 183
9.1 Introduction 183
9.2 Reference Conditions and Defining Thresholds 184
9.3 Volume Control 184
9.3.1 Runoff Depth 184
9.3.2 Curve Number Reduction 185
9.4 Peak Flow, Flow, and Geomorphology 186
9.5 Pollutant Percent Removal 189
9.6 Chesapeake Bay Retrofit Curves 190
9.7 Target Effluent Concentrations 190
9.8 Annual Mass Load 192
9.9 Probability and Exceedance 193
9.10 Pollutant Durations 195
References 198
Problems 199
10 Preventing Runoff and Stormwater Pollution 201
10.1 Introduction 201
10.2 Site Design and Low Impact Development 201
10.3 Compacted Urban Surfaces 203
10.3.1 Avoiding Compaction and Promoting Infiltration 204
10.3.2 Soil Restoration 204
10.3.3 De-paving 205
10.3.4 Removing Abandoned Housing 205
10.4 Street Trees 206
10.5 Disconnecting Impervious Surfaces 207
10.5.1 Defining Disconnected Impervious Surface 208
10.5.2 Calculating the Benefit of Disconnecting Imperviousness 208
10.5.3 Design 210
10.5.4 Water-Quality Benefits 212
10.5.5 Performance Results 212
10.6 Pollution Prevention 213
10.6.1 Street Sweeping 213
10.6.2 Product Prohibition 216
10.7 Education 217
References 217
Problems 218
11 Green Infrastructure Stormwater Control 221
11.1 Introduction 221
11.2 Fundamentals of Stormwater Control Measures 221
11.3 Designing to Climate and the Watershed 222
11.4 Types of Stormwater Control Measures 223
11.5 Nonvegetated Stormwater Control Measures 224
11.5.1 Infiltration Basins and Rock Beds 224
11.5.2 Permeable Pavements 224
11.5.3 Cisterns and Rain Barrels 225
11.5.4 Sand Filters 225
11.6 Vegetated Stormwater Control Measures 225
11.6.1 Vegetation Challenges 227
11.6.2 Green Roofs 229
11.6.3 Bioretention 230
11.6.4 Vegetated Swales and Filter Strips 230
11.6.5 Stormwater Wetlands 230
11.7 Selecting the SCM Site 230
11.8 Stormwater Treatment Media 231
11.8.1 Rock, Gravel, and Coarse Sand 232
11.8.2 Silts and Clays 232
11.8.3 Organic Media 232
11.9 Volumetric Storage 233
11.10 Drains and Underdrains 234
11.11 “Irreducible Concentrations” 235
References 237
Problems 238
12 Inlets, Bypasses, Pretreatment, and Proprietary Devices 239
12.1 Introduction 239
12.2 Inlets 239
12.3 Stormwater Bypass 240
12.4 Catch Basin and Inlet Filters 241
12.5 Pretreatment 242
12.6 Forebays 242
12.6.1 Forebay Design 243
12.6.2 Forebay Maintenance 245
12.7 Proprietary Devices 246
12.8 Accumulated Trash and Sediment 248
References 249
Problems 249
13 Green Roofs 251
13.1 Introduction 251
13.2 Climate and Green Roofs 251
13.3 Types of Roofs 252
13.3.1 Green Roofs 252
13.3.2 Blue Roofs 253
13.4 Extensive Green Roof Components 256
13.5 Hydrologic Design Strategies 259
13.5.1 Rainfall Capture 259
13.5.2 Evapotranspiration 262
13.6 Water Quality Design 264
13.6.1 Phosphorus 265
13.6.2 Nitrogen 266
13.6.3 Metals 266
13.7 Inspection and Maintenance 266
13.8 Other Green Roof Benefits 266
References 267
Problems 268
14 Rainwater Harvesting 271
14.1 Introduction 271
14.2 Potential as a Water Resource 272
14.3 Harvested Roof Water Quality 273
14.4 Rain Barrels 274
14.5 Rainwater Harvesting Regulations 275
14.5.1 Non-stormwater Regulations 276
14.5.2 Stormwater Regulations 276
14.6 Designing Rainwater Harvesting Systems 277
14.6.1 General Characteristics and Purpose 277
13.6.2 Rainwater Storage Sizing Techniques 278
14.6.3 Design 279
14.7 Designing for Enhanced Stormwater Performance 282
14.7.1 Passive Release Mechanism 282
14.7.2 Active Release Mechanism 284
14.7.3 Alternative Approaches for Irrigation-based Systems 285
14.7.4 Designing an Infiltration or Filtration Area 286
14.8 Treatment for High-quality Use 288
14.9 Inspection and Maintenance 289
References 289
Problems 290
15 Permeable Pavement 293
15.1 Introduction 293
15.2 Types of Permeable Pavements 295
15.3 Permeable Pavement Installation 298
15.4 Designing for Infiltration and Percolation 298
15.4.1 Surface Infiltration 299
15.4.2 Run-on Ratio 299
15.4.3 Depth/Volume of Storage Layer 301
15.4.4 Underdrain Need 301
15.4.5 Underdrain Configuration 301
15.4.6 In Situ Soils 302
15.5 Permeable Pavement Hydrologic Design Strategies 302
15.6 Permeable Pavement Hydrology 305
15.6.1 Hydrographs 305
15.6.2 Curve Numbers and Storage 306
15.6.3 Evaporation 307
15.7 Water Quality Design 307
15.7.1 Particulate Matter 308
15.7.2 Metals 308
15.7.3 Nutrients 308
15.7.4 Hydrocarbons 309
15.7.5 pH 309
15.7.6 Thermal Pollution (Temperature) 310
15.7.7 Pollutant Loads 310
15.7.8 Long-term Pollutant Fate 311
15.8 Maintenance 312
15.9 Design Summary 312
15.10 Permeable Pavement Cost Factors 312
15.11 Permeable Friction Course 314
References 315
Problems 317
16 Infiltration Trenches and Infiltration Basins 319
16.1 Introduction 319
16.2 Types of Basins 319
16.3 Mechanisms of Treatment 321
16.4 Infiltration 323
16.5 Surface Infiltration Basins 323
16.6 Infiltration Trench and Subsurface Infiltration Basin Design 326
16.7 Infiltration Trench and Basin Performance 327
16.8 Inspection and Maintenance 328
References 329
Problems 329
17 Sand Filters 331
17.1 Introduction 331
17.2 Basic Sand Filter Operation 331
17.3 Sand Filter Options and Configurations 331
17.4 Sand Filter Design 333
17.5 Water Quality Performance 335
17.5.1 Particulate Matter Removal 335
17.5.2 Dissolved Pollutant Removal 336
17.6 Sand Filter Headloss 336
17.7 Solids Accumulation and Clogging 337
17.8 Sorptive and Reactive Media 339
17.9 Geotextile Filters 339
17.10 Inspection and Maintenance 340
References 340
Problems 341
18 Bioretention 343
18.1 Introduction 343
18.2 Bioretention Classifications 344
18.3 Bioretention Components 345
18.4 Siting and Configuration 346
18.5 Bioretention Flow Entrances, Inlets, and Forebays 348
18.6 Storage Bowl 350
18.7 Bioretention Design: Static Storage and Hydrologic Performance 351
18.8 Dynamic Storage 353
18.9 The Media 354
18.9.1 Rain Gardens 354
18.9.2 Standard Media 354
18.9.3 Surface Mulch Layer 354
18.10 Evapotranspiration 355
18.11 The Media and Particulate Matter Removal 356
18.12 The Media and Heavy Metals Removal 358
18.13 The Media and Organic Pollutants Removal 359
18.14 The Media and Phosphorus Removal 360
18.14.1 Phosphorus Removal in Bioretention 361
18.14.2 Quantifying Phosphorus Removal 362
18.14.3 Media Enhancements for Phosphorus Removal 363
18.15 The Media and Nitrogen Removal 366
18.15.1 Nitrogen Processing in Standard Bioretention Systems 366
18.15.2 Enhanced Nitrogen Removal 368
18.15.3 Biological Nitrogen Transformations 368
18.16 The Media and Bacteria Removal 370
18.17 Vegetation 370
18.18 The Underdrain and Subsurface Storage 373
18.19 Internal Water Storage and Nitrogen Removal 376
18.20 Bioretention Pollutant Load Reductions 377
18.21 Bioretention Exfiltration and Groundwater 380
18.22 Inspection and Maintenance 380
References 381
Problems 386
19 Swales, Filter Strips, and Level Spreaders 393
19.1 Introduction 393
19.2 Characteristics 393
19.2.1 Swales 393
19.2.2 Filter Strips and Level Spreaders 393
19.3 Swale Design 394
19.3.1 Configurations 396
19.3.2 Hydraulic Design 396
19.4 Filter Strip Design 399
19.4.1 Configurations 399
19.4.2 Flow Conveyance 399
19.5 Filter Strips Conveying to Swales 400
19.6 Water Quality Considerations 402
19.6.1 Designing for Pollutant Capture: Length of Swale 402
19.6.2 Designing for Particulate Matter Removal 402
19.6.3 Designing for Particulate Matter Removal with Particle-size Distribution Available 405
19.6.4 Designing for Metals Removal 406
19.6.5 Filtration through Swales and Filter Strips 408
19.6.6 Check Dams 409
19.7 Swale Performance 410
19.7.1 Hydrologic Considerations 410
19.7.2 Water Quality Considerations 412
19.8 Construction, Inspection, and Maintenance 414
19.9 Summary 414
References 415
Problems 416
20 Stormwater Wetlands 421
20.1 Introduction 421
20.2 Sizing Stormwater Wetlands 422
20.3 Stormwater Wetland Features and Design 423
20.3.1 Zone I - Deep Pools 424
20.3.2 Zone II - Deep to Shallow Water Transition Zone (Transition Zone) 426
20.3.3 Zone III - Shallow Water Zone 426
20.3.4 Zone IV - Temporary Inundation Zone 427
20.3.5 Zone V - Upper Bank 428
20.4 Wetland Vegetation 428
20.5 Wetland Soils and Vegetation Growth Media 430
20.6 Wetland Outlet Configuration 431
20.7 Wetland Construction 437
20.8 Wetland Variations 437
20.8.1 Wetland Design for Cold Water Species (Salmonids) 437
20.8.2 Off-line Stormwater Wetlands 437
20.8.3 Wetlands with High Flow Bypass 438
20.9 Water Quality Improvements in Stormwater Wetlands 439
20.10 Other Stormwater Wetland Designs 442
20.10.1 Submerged Gravel Wetlands 442
20.10.2 Ponds Transitioning to Wetlands 443
20.10.3 Floating Wetlands 444
20.11 Inspection and Maintenance 447
References 447
Problems 449
21 Putting It All Together 451
21.1 Introduction 451
21.2 SCM Hydrologic Performance Summary 451
21.3 SCM Water Quality Performance Summary 453
21.3.1 Green Roofs and Water Harvesting 453
21.3.2 Permeable Pavements 453
21.3.3 Infiltration Basins 454
21.3.4 Sand Filters 454
21.3.5 Bioretention 454
21.3.6 Vegetated Swales 455
21.3.7 Stormwater Wetlands 455
21.4 Treatment Trains 455
21.5 SCM Treatment Train Examples 456
21.5.1 Treatment Trains within Individual SCMs 456
21.5.2 Incorporating Treatment Trains in Traditional SCMs 457
21.5.3 SCMs in Series 457
21.6 Quantifying Performance in SCM Treatment Trains 462
21.7 Real Time Controls 463
21.8 Designing for Climate Change 464
21.9 Greener Infrastructure: What Does the Future Hold? 466
References 467
Problems 469
Appendix A 471
Index 473
