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 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

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 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

4 694 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 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

5 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 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

6 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) 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

7 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 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

8 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)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 Head Losses for Junction Boxes, Manholes, and Bends Figure Outlet Control Headwater for Culvert with Free SurfaceFigure Outlet Control, Fully Submerged FlowFigure Point at Which Free Surface Flow BeginsTablesTable Probability of ExceedanceTable DESIGN Storms for DRAINAGE ElementsTable Runoff Coefficients for Zoned AreasTable Runoff Coefficients for Non-Zoned AreasTable Roughness Coefficients (Manning s n)

9 For Sheet FlowTable Runoff Curve NumbersTable Composite Curve Number ExampleTable Sustainable DRAINAGE Measure Curve NumbersTable Encroachment LimitsTable Inlet TypesTable Frequencies for Coincidental OccurrencesTable Outlet Depth ConditionsTable Entrance Loss CoefficientsTable Riprap Apron Length Downstream of Drop StructuresTable Maximum Channel VelocitiesTable Minimum Crown Width of EmbankmentsTable Constructed Wetland Volume RatiosTable Constructed Wetland Area RatiosTable Easement WidthsDallas DRAINAGE DESIGN ManualviiFigure Headwater due to Full Flow at Inlet and Free Surface at OutletFigure Cross Sectional Area Based on Full FlowFigure Culvert with Overtopping FlowFigure Over-Embankment Flow Adjustment FactorFigure Roadway Overtopping with High TailwaterFigure Cross Section of Flow Over RoadwayFigure Typical Performance CurveFigure Momentum Function and Specific EnergyFigure Determination of Sequent DepthFigure Solution for Circula