Low Impact Development and Sustainable Stormwater Management

Prologue: Habitat, Sustainability, and Stormwater Management xi Acknowledgments xiii 1 Rainwater as the Resource 1 1.1 The Water Balance as a Guide for Sustainable Design 1 1.2 The Water Balance by Region 7 1.3 Arid Environments: The Southern California Model 11 The Energy Demand for Water in Southern California 13 1.4 The Altered Water Balance and Hydrologic Impacts 16 Imperviousness 16 Increased Volume of Runoff 20 1.5 The Impacts of Development on the Hydrologic Cycle 24 Reduced Groundwater Recharge 24 Reduced Stream Base Flow 25 Altered Stream Channel Morphology 26 Water Supply Impacts 26 1.6 The Historic Approach: Detention System Design 27 1.7 Stormwater Volume Methodologies 30 2 Stormwater Hydrology and Quality 33 2.1 Overland Flow: The Beginning of Runoff 33 2.2 Regional Hydrology 35 Wetlands 36 First-Order Streams 38 2.3 Stormwater Volume 39 2.4 The Water Quality Impacts of Land Development 40 Increased Pollutants in Urban Runoff 43 2.5 The Chemistry of Urban Runoff Pollution 44 2.6 Understanding Pollutant Transport in Stormwater 47 Stormwater Quantity and Quality 47 Particulates 48 Solutes 49 3 Land as the Resource 51 3.1 Historic Patterns of Land Development 51 3.2 Sustainable Site Design 58 3.3 Watershed Setting and Physical Context 58 3.4 Smart Growth Issues 59 Changes Related to Development 59 3.5 Conflict between Desired Land Use and Sustainability 61 3.6 Physical Determinants of Land Development 62 Geology 62 Physiography 65 Topography 66 Soil and Subsurface Conditions 67 3.7 Urban Communities with Combined Sewer Overflows 68 End of the Sewer 71 Other Urban Infrastructure 73 3.8 The Living Building and Zero Net Water Use 74 4 The Planning Process for LID 79 4.1 Sustainable Site Planning Process with Stormwater Management 79 Guideline 1: Understand the Site 79 Guideline 2: Apply LID Conservation Design 80 Guideline 3: Manage Rainfall Where It Originates 81 Guideline 4: Design with Operation and Maintenance in Mind 83 Guideline 5: Calculate Runoff Volume Increase and Water Quality Impacts 85 4.2 Overview of the Site Design Process for LID 86 5 The Legal Basis for LID: Regulatory Standards and LID Design Criteria 95 5.1 The Land–Water Legal Process 95 Common Law 95 Federal Water Quality Law 96 Federal Land Use Law 97 5.2 The Evolution of Land Development Regulation 98 5.3 The Regulatory Framework 100 Pennsylvania Land Use Law 101 Pennsylvania Water Law 102 California Land Use Law 103 California Water Law 104 5.4 Stormwater Management Regulations 105 Volume Control 105 Volume Control Criteria 106 Volume Control Guideline 108 Peak-Rate Control Guideline 108 Water Quality Protection Guideline 109 Stormwater Standards for Special Areas 110 Legal Implications of Green Infrastructure 110 6 LID Design Calculations and Methodology 113 6.1 Introduction to Stormwater Methodologies 113 6.2 Existing Methodologies for Runoff Volume Calculations 114 Runoff Curve Number Method 114 Small Storm Hydrology Method 117 Infiltration Models for Runoff Calculations 119 Urban Runoff Quality Management 119 6.3 Existing Methodologies for Peak-Rate/Hydrograph Estimates 120 The Rational Method 120 The NRCS (SCS) Unit Hydrograph Method 120 6.4 Computer Models 121 The HEC Hydrologic Modeling System 121 The SCS/NRCS Models: WinTR-20 and WinTR-55 121 The Stormwater Management Model 122 The Source Loading and Management Model 122 Continuous Modeling 123 6.5 Precipitation Data for Stormwater Calculations 123 6.6 Accounting for the Benefits of LID: Linking Volume and Peak Rate 124 6.7 Recommended LID Stormwater Calculation Methodology 124 Methods Involving No Routing 125 Methods Involving Routing 126 6.8 Nonstructural BMP Credits 127 7 Design of LID Systems 131 7.1 Nonstructural Measures 131 Impervious Surface Reduction 131 Limitation of Site Disturbance 132 Site Design with Less Space 132 7.2 Structural Measures 133 7.3 Pervious Pavement with an Infiltration or Storage Bed 134 Types of Porous Pavement 134 Description and Function 136 Pervious Bituminous Asphalt 141 Pervious Portland Cement Concrete 141 Pervious Paver Blocks 141 Reinforced Turf 143 Other Porous Surfaces 144 Potential Applications 144 Pervious Pavement Walkways (Concrete and Asphalt) 144 Rooftop and Impervious Area Connections 144 Water Quality Mitigation 145 7.4 Bioremediation 145 Rain Garden: Design and Function 146 Primary Components of a Rain Garden System 147 7.5 Vegetated Roof Systems 152 Design and Function 154 Design Elements of a Vegetated Roof System 155 Types of Vegetated Roof Systems 155 Dual Media with a Synthetic Retention Layer 158 Potential Applications 158 7.6 Capture–Reuse 158 Rain Barrels and Cisterns 161 Vertical Storage 164 8 Structural Measures: Construction, Operation, and Maintenance 169 8.1 Porous Pavement Systems 169 Construction 169 Storage/Infiltration Bed Dimensions 174 Construction Staging 174 Operation and Maintenance 176 Vacuuming 177 Restoration of Porous Pavements 178 Cost of Porous Pavement 178 8.2 Bioremediation Systems 179 Rain Gardens 179 Construction of a Rain Garden 183 Maintenance of Rain Gardens 183 Cost of Rain Gardens 184 Vegetated Roof Systems 184 Construction of a Vegetated Roof 187 Maintenance of Vegetated Roofs 188 Cost of Vegetated Roofs 188 8.3 Capture–Reuse Systems 188 Construction 188 Volume Reduction 191 Peak-Rate Mitigation 191 Water Quality Mitigation 191 Appendix A: The Stormwater Calculation Process 193 Appendix B: Case Studies 213 B.1 The Transition from Research to Practice 213 B.2 Manuals 215 B.3 LID Manual for Michigan (2008) 219 B.4 Models and Watershed Studies 237 B.5 Design and Construction Projects 251 Index 283