DRAINAGE DESIGN MANUAL - Dallas

1 DRAINAGE DESIGN MANUALCITY OF Dallas SEPTEMBER 2019 City of DallasDRAINAGE DESIGN MANUALSEPTEMBER 2019 Dallas DRAINAGE DESIGN ManualiContentsSECTION 1 INTRODUCTION 11 1 PURPOSE 21 2 SCOPE 21 3 OVERVIEW 31 4 INTEGRATING DRAINAGE 41 4 1 DRAINAGE DESIGN Process 41 4 2 DRAINAGE DESIGN Considerations 41 4 3 Defining a Project 51 4 4 Sustainable DESIGN Guidelines 51 4 5 Pre-Development Meeting 51 4 6 DESIGN Software 5 SECTION 2 HYDROLOGY 72 1 GENERAL 82 2 HYDROLOGY 92 2 1 Rational Formula 92 2 1 1 Runoff C Value 92 2 1 2 Rainfall Intensity (i) 102 2 1 3 Time of Concentration (Tc)

2 102 2 2 Hydrograph Methods 122 2 2 1 SCS Unit Hydrograph Method 122 2 2 2 Use of Other Hydrograph Methods 142 2 2 3 Flood Routing 152 2 2 4 Hydrograph Time Interval Determination 152 2 2 5 Gage Data and Calibration Methods 162 2 2 6 Storage Options 162 3 DETENTION / RETENTION ANALYSIS 162 3 1 DESIGN Objectives 162 3 2 Downstream Analysis 172 3 3 DESIGN Methodology 172 3 3 1 Modified Rational Method 172 3 3 2 Adjustment for Sustainable DRAINAGE Measures 182 3 4 Water Rights 19 SECTION 3 ROADWAY DRAINAGE DESIGN 213 1 GENERAL 223 2 IMPROVED ROADWAY DRAINAGE 223 2 1 Street Capacity 223 2 2 Straight Crown Street 233 2 3 Parabolic Crown Street 233 2 4 Valley Gutter Flow 233 2 5 Flow in Alleys 243 3 INLET DESIGN 243 3 1 Types of Inlets 243 3 1 1 Grate Inlet 253 3 1 2 Curb Inlet 253 3 1 3 Y-Inlet 253 3 1 4 Combination Inlet 253 3 1 5 Slotted Drain Inlet 263 3 2 Inlet DESIGN Requirements 263 3 3 Inlet Capacity Calculations 273 3 3 1

3 Grate Inlet 273 3 3 2 Curb Inlet 293 3 3 3 Y-Inlet 303 3 3 4 Combination Inlet 313 3 3 5 Slotted Drain Inlet 313 4 UNIMPROVED ROADWAY DRAINAGE 313 4 1 Bar Ditch DESIGN 313 4 2 Bioswales / Bioretention Swales 313 4 2 1 Bioswales 313 4 2 2 Bioretention Swales 323 4 3 Culvert Crossing 323 5 ADDITIONAL ROADWAY DRAINAGE CONSIDERATIONS 333 5 1 Utility and DRAINAGE Infrastructure Requirements 333 5 2 Alternative Pavements 343 5 2 1 General DESIGN Considerations 343 5 2 2 Permeable Paving 343 5 2 3 Permeable Unit Pavement System 353 5 2 4 Porous Pavers 363 5 3 sand and Organic Media Filters 37iiTable of Contents3 6 ENCLOSED STORM DRAIN SYSTEM DESIGN 393 6 1 Starting Hydraulic Gradeline Elevation 393 6 2 Storm Drain Line DESIGN 403 6 3 Lateral DESIGN 413 6 4 Head Losses 413 6 5 Manhole Placement and DESIGN 423 6 6 Tree Box Filters 423 7 CULVERT HYDRAULIC DESIGN 443 7 1 General 443

4 7 2 DESIGN Frequency 443 7 3 Hydraulic Controls 443 7 3 1 Inlet Control 443 7 3 2 Outlet Control 443 7 4 Energy Gradient Analyses 453 7 4 1 Energy Loss Through Culvert 453 7 4 2 Energy Balance at Inlet 493 7 4 3 Determination of Outlet Velocity 503 7 4 4 Depth Estimation Approaches 503 7 4 5 Direct Step Backwater Method 503 7 4 6 Roadway Overtopping 503 7 4 7 Performance Curves 513 7 4 8 Exit Loss Considerations 513 7 5 Flow Regime Determination 513 7 5 1 Subcritical Flow and Steep Slope 513 7 5 2 Supercritical Flow and Steep Slope 523 7 5 3 Hydraulic Jump in Culverts 523 7 5 4 Sequent Depth 523 7 6 Other Culvert DESIGN Considerations 523 8 OUTFALL DESIGN 543 8 1 General 543 8 2 Headwalls / Pipe End Treatment 553 8 3 Energy Dissipators 553 8 3 1 Riprap Aprons / Basins 553 8 3 2 Concrete Aprons / Basins 613 8 3 3 Baffle Blocks 613 8 3 4 Baffled Outlets 613 8 3 5 Drop Structures 633 8 3 6 Other Energy Dissipators 633 8 4 Sedimentation Basin 63 SECTION 4 BRIDGE HYDRAULIC DESIGN 654 1 GENERAL 664 2 DESIGN FREQUENCY AND FREEBOARD 664 2

5 1 DESIGN Frequency 664 2 2 Freeboard / Minimum Clearance 674 3 FLOW REGIMES 674 3 1 Low Flow Considerations 674 3 2 High Flow Considerations 684 3 3 Supercritical Flow 684 3 4 Erosive Velocities 684 4 CHANNEL CONSTRICTION 684 5 SCOUR 694 6 BRIDGE DECK DRAINAGE 694 7 ROADWAY OVERTOPPING 704 8 OTHER DESIGN CONSIDERATIONS 70 SECTION 5 OPEN CHANNEL DESIGN 735 1 GENERAL 745 2 OPEN CHANNEL HYDRAULICS 745 2 1 Flow Classification 745 2 1 1 Types of Flow in Open Channels 745 2 1 2 Subcritical Flow 755 2 1 3 Supercritical Flow 755 2 1 4 Critical Flow 755 2 1 5 Hydraulic Jump 765 2 1 6 Uniform Flow 765 3 DESIGN GUIDELINES 785 3 1 Manning s n Values 785 3 2 DESIGN Frequency and Freeboard 785 3 3 Channel Velocity 785 3 4 Channelization 785 3 5 Channel Geometry 785 3 6

6 Channel Slope 795 3 7 Bed Controls 795 3 7 1 Channel Drops 795 3 7 2 Baffle Chutes 795 3 7 3 Checkdams 80 Dallas DRAINAGE DESIGN Manualiii5 3 8 Channel Bends 805 3 9 Channel Junctions 815 3 10 Bottom Width Transition 815 3 11 Superelevation 81 SECTION 6 DRAINAGE STORAGE DESIGN 836 1 GENERAL 846 2 DETENTION BASIN 856 2 1 DESIGN Guidance 856 2 2 Low Flow Channels / Pilot Channels 866 3 RETENTION BASIN 876 4 UNDERGROUND DETENTION 876 5 STORMWATER PONDS 886 6 CONSTRUCTED WETLANDS 896 7 RAINWATER HARVESTING 916 8 RAIN GARDENS 926 9 BIORETENTION 946 10 INFILTRATION REQUIREMENTS AND TESTING 956 11 STORMWATER PUMP STATION DESIGN 966 11 1 DESIGN Guidance 966 11 1 1 Pump Station Hydrology 966 11 1 2

7 Pump Station Hydraulics 976 11 1 3 Operation and Maintenance 97 SECTION 7 EROSION AND SEDIMENT CONTROL MEASURES 997 1 GENERAL 1007 2 NATURAL CHANNEL SETBACK 1007 3 TEMPORARY CONSTRUCTION EROSION CONTROL 1027 4 PERMANENT EROSION CONTROL DESIGN 1027 4 1 Grass / Vegetation 1027 4 2 Turf Reinforcement 1027 4 3 Bioengineering 1027 4 4 Stone Riprap DESIGN 1047 4 5 Gabions 1057 4 6 Concrete 1057 4 7 Concrete Block Mats 1057 4 8 Retaining Walls in Waterways 105 SECTION 8 FLOODPLAIN AND SUMP DESIGN REQUIREMENTS 1098 1 GENERAL 1108 2 FLOODPLAIN HYDRAULIC ANALYSIS 1108 2 1 Hydraulic Modeling 1118 2 1 1 1D Steady Flow Modeling 1118 2 1 2 1D Unsteady Flow Modeling 1118 2 1 3 2D Unsteady Flow Modeling 1118 3 REGULATORY FLOODPLAIN MAPS 1128 4 FLOODPLAIN APPROVAL PROCESS 1128 4 1 Fill Permits 1128 4 2 Sump Fill Permits 1138 4 3 Floodplain Alteration Permits

8 1138 4 4 Other City Permits 1138 5 ENHANCEMENTS AND RECREATIONAL USES 1138 6 FEMA COORDINATION 1148 7 SUMP AND LEVEE AREAS 1148 7 1 Sumps 1148 7 2 Levee Setback 114 SECTION 9 OTHER REGULATORY REQUIREMENTS 1179 1 GENERAL 1189 2 ENVIRONMENTAL AND CONSTRUCTION PERMITTING REQUIREMENTS 1189 2 1 Water Quality 1189 2 2 Tree Mitigation 1189 2 3 Section 404 Permitting 1199 2 4 Section 408 Permitting 1199 2 5 Aquatic Relocation 1199 2 6 Construction Permit Requirements 1199 2 6 1 TPDES Construction General Permi