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 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

3 333 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 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

4 FREEBOARD 664 2 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 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

5 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 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

6 Permits 1138 4 3 Floodplain Alteration Permits 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 Permits 1199 2 6 2 City Grading and Fill Permits 1199 2 6 3 Floodway Access Permits 1199 3 EASEMENTS 1209 3 1 Storm Sewer Line Easements 1209 3 2 Detention / Retention Area Easements 1209 3 3 Access Easements 1209 3 4 Slope Easements 120ivTable of Contents9 3 5 Subsurface Easements (Tunnels / Tieback Anchors)

7 1219 3 6 Utility Considerations 1219 4 COORDINATION WITH OTHER AGENCIES 1219 4 1 County Requirements 1219 4 2 NCTCOG1219 4 3 TCEQ1229 4 4 TxDOT1229 4 5 USACE1229 4 6 Texas Parks & Wildlife 1229 4 7 FEMA1229 4 8 DART and Other Rail Systems 1229 4 9 Neighboring Cities 123 SECTION 10 SUBMITTAL REQUIREMENTS 12510 1 GENERAL 12610 2 PLATTING / DEDICATION OF WATER COURSES AND BASINS 12610 3 DOCUMENTATION REQUIREMENTS 12710 3 1 DRAINAGE Reports 12710 3 2 Survey12810 3 2 1 Outfall Ditches Less Than 3ft Wide 12810 3 2 2 Outfall Ditches More Than 3ft Wide 12910 3 2 3 Culverts13010 3 2 4 DRAINAGE Pipes 13010 3 2 5 Minor Headwalls and Wingwalls 13010 3 2 6 Inlet Structures 13110 3 2 7 Floodplain Surveys 13110 4 CONSTRUCTION PLAN PREPARATION 13110 4 1 General13110 4 2 Conceptual DESIGN Phase 13110 4 2 1 Checklist for Conceptual DESIGN Phase 13210 4 3 Preliminary DESIGN Phase 13210 4 4 Pre-Final DESIGN Phase 13210 4 5 Final DESIGN Phase 13210 4 6 Drafting Requirements 13310 4 7 Plan Requirements 13310 4 7 1 DRAINAGE Area Map 13310 4 7 2 Plan / Profile Sheets 13310 4 7 3 Special Details 135 SECTION 11 OPERATION AND MAINTENANCE 13711 1 OPERATION AND MAINTENANCE CONSIDERATIONS 13811 2 OPERATION AND MAINTENANCE PLANS 138 APPENDICES 141A 1 GENERAL 142A 1 1 Applicable Regulations142A 1 2 List of Acronyms and Abbreviations143A 1 3 Glossary of Terms and Definitions143A 1 4 Sources146A 2 HYDROLOGY 147A 2 1 C Adjustment

8 Factor Example147A 3 HYDRAULICS 148A 3 1 Sag Inlet DESIGN Worksheet149A 3 2 Manning s n for Channels150A 3 3 Manning s n for Closed ConduitsFlowing Partly Full153A 3 4 Gutter Flow / Inlet Computations155A 3 5 Full Flow Coefficient Values156A 3 5 1 Elliptical Concrete Pipe156A 3 5 2 Concrete Arch Pipe157A 3 5 3 Precast Concrete Box Section158A 3 5 4 Circular Concrete Pipe159A 3 6 Energy Equations in Open Channels160A 3 6 1 Energy160A 3 6 2 Specific Energy160A 3 6 3 Froude Number160A 4 PROCEDURES 161A 5 SUBMITTAL REQUIREMENTS AND FORMS 161A 5 1 Checklist for Storm DRAINAGE Plans161A 5 2 Non-Standard Material Agreement Template 164A 6 OTHER 167A 6 1 Materials Matrix168A 6 2 Media172A 6 3 Seed Mixes172A 6 4 Recommended Plants180A 6 5 Operation and Maintenance Plan185A 6 6 Annual Maintenance Schedule186A 6 7 Maintenance Records186 Dallas DRAINAGE DESIGN ManualvA 7 FIGURES 186A 7 1 Capacity of Triangular Gutters 187A 7 2 Parabolic Crown Street Flow Capacity 188A 7 3 Alley Conveyance Without Curb 190A 7 4 Alley Conveyance With Curb 191A 7 5 Curves for Determining the Critical Depth in Open Channels 192A 7 6 Section 2 Figures 193A 7 7 Section 3 Figures 195A 7 8 Section 5 Figures 205viTable of ContentsFiguresFigure DRAINAGE DESIGN ProcessFigure Shallow Concentrated Flow Average VelocityFigure Areal Reduction Factors for Small Watersheds for 50% AEP or Greater 1-day DESIGN StormsFigure Process for C Value Adjustment Figure Dry Lane (Allowable Lane Encroachment)

9 Figure Parabolic Crown Street Flow CapacityFigure Grate InletFigure Curb InletFigure Y-InletFigure Combination InletFigure Slotted Drain InletFigure Storm Drain InletsFigure Grate PerimeterFigure Curb Inlets on Grade: Ratio of Intercepted to Total FlowFigure Y-Inlet Capacity Curves at Sag PointFigure Utility in Typical StreetsFigure Permeable Unit Pavement SystemFigure Sand & Organic Media FiltersFigure Hydraulic GradientFigure Wye Connection DetailFigure Head Losses in Laterals, Wyes, and EnlargementsFigure Hea