THE CITY OF SAN DIEGO Transportation & Storm Water Design Manuals Drainage Design Manual January 2017 Edition The City of San Diego | Drainage Design Manual | January 2017 Edition DRAINAGE DESIGN MANUAL THIS PAGE INTENTIONALLY LEFT BLANK FOR DOUBLE-SIDED PRINTING The City of San Diego | Drainage Design Manual | January 2017 Edition CONTENT Contents Contents ............................................................................................................................................................... i Figures ............................................................................................................................................................... vii Tables .................................................................................................................................................................. ix Equations ............................................................................................................................................................. x 1. Introduction.............................................................................................................................................. 1-1 Policies ............................................................................................................................................... 1-1 Basic Objectives ......................................................................................................................... 1-2 Exceptions to Design Standards .............................................................................................. 1-2 Basic Policy in Drainage Design ............................................................................................... 1-3 Cooperative Drainage Project .................................................................................................. 1-3 Update of Design Standards .................................................................................................... 1-3 Drainage Report and Green Infrastructure Sizing Reports ......................................................... 1-3 Use of Standard Drawings ............................................................................................................... 1-4 2. Hydrology ................................................................................................................................................. 2-1 Discharge Flow Methods ................................................................................................................. 2-1 Design Storm Frequency ................................................................................................................. 2-1 Soil Type ............................................................................................................................................. 2-2 Other Requirements ........................................................................................................................ 2-2 Water Quality Considerations ......................................................................................................... 2-2 3. Street Drainage, Cleanouts, and Inlets ................................................................................................. 3-1 Design Criteria ................................................................................................................................... 3-1 Roadway Drainage..................................................................................................................... 3-1 Inlets ............................................................................................................................................ 3-2 Design Procedure ............................................................................................................................. 3-5 Gutter Flow ................................................................................................................................. 3-5 Inlet Design ................................................................................................................................. 3-8 4. Storm Drains ............................................................................................................................................ 4-1 Design Criteria ................................................................................................................................... 4-1 Hydraulic Capacity ..................................................................................................................... 4-1 Manning Roughness Coefficient .............................................................................................. 4-1 Alignment and Curvature ......................................................................................................... 4-2 Cleanouts .................................................................................................................................... 4-3 Deep-Cover Conduits and Culverts ......................................................................................... 4-5 Easements and Access Roads .................................................................................................. 4-6 Water-Tight Joints ...................................................................................................................... 4-8 Slope Drains ............................................................................................................................... 4-9 Pipe Design Life ....................................................................................................................... 4-10 Storm Drain Plans ............................................................................................................... 4-11 Hydraulic Design of Storm Drains ................................................................................................ 4-11 Minimum Gradient .................................................................................................................. 4-11 Basic Design Procedure .......................................................................................................... 4-12 Storm Drain Analysis – Uniform Flow ................................................................................... 4-13 Storm Drain Analysis – Pressure Flow .................................................................................. 4-14 Storm Drain Analysis - HGL Calculations .............................................................................. 4-14 Downstream Control (Tailwater) Elevation .......................................................................... 4-15 i The City of San Diego | Drainage Design Manual | January 2017 Edition CONTENT Energy Loss Calculations ........................................................................................................ 4-16 5. Culverts and Low Water Crossings........................................................................................................ 5-1 General Design Criteria .................................................................................................................... 5-1 Hydraulic Criteria ....................................................................................................................... 5-1 6. Site Drainage ............................................................................................................................................ 6-1 General Design Criteria .................................................................................................................... 6-1 7. Open Channels ........................................................................................................................................ 7-1 Types of Open Channels .................................................................................................................. 7-1 Natural and Designed Alluvial-Bed Channels ........................................................................ 7-1 Grass-Lined Channels ............................................................................................................... 7-2 Wetland-Bottom Channels ....................................................................................................... 7-2 Riprap- or Cobble-Lined Channels .......................................................................................... 7-3 Concrete-Lined Channels ......................................................................................................... 7-4 Other Types of Channel Lining ................................................................................................ 7-4 Selection of Channel Type ........................................................................................................ 7-5 General Design Criteria .................................................................................................................... 7-5 Hydraulic Capacity ..................................................................................................................... 7-5 Manning Roughness Coefficient .............................................................................................. 7-5 Uniform Flow .............................................................................................................................. 7-5 Vertical and Horizontal Alignment .........................................................................................