District of Columbia

District of Columbia Stormwater Management Guidebook

CityDistrict of ColumbiahighNo

Open source PDF ↗Official agency page ↗

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Document Metadata

Jurisdiction level

municipality

“The PROW occupy approximately 25 percent of the impervious area of the District of Columbia”
Appendix B

State

District of Columbia

“Hydrologic Soil Groups approved for use in the District are contained in the Soil Survey of the District of Columbia Handbook.”
Appendix H, Page H-2

Version / edition

Appendices A–U, changes accepted July 29, 2013

“FinalGuidebook_changes accepted_Appendices A-U_07_29_2013”
Source filename

Adoption / effective date

2013-07-29

“FinalGuidebook_changes accepted_Appendices A-U_07_29_2013”
Source filename

Last revised date

Not found in document

No evidence cited

Relationship to state manual

independent

“DDOE's Stormwater Management Guidebook (SWMG)”
Appendix E

Design Criteria

Design storm return periods (years)

2-year, 15-year, 100-year

“Detention is required to reduce the peak discharge rate from the 2-year storm event to the preproject peak discharge rate ... discharge rate from the 15-year storm event”
Appendix A, Design Examples

Water quality volume method

Stormwater Retention Volume (SWRv) is calculated as P/12 × Rv × SA, where P is a percentile rainfall depth that varies by project type (90th percentile, 1.2 inches for major land-disturbing activities; 80th percentile, 0.8 inches for major substantial improvements; 85th percentile, 1.0 inches for major substantial improvements in the Anacostia Waterfront Development Zone). In the AWDZ, Water Quality Treatment Volume (WQTv) uses the 95th percentile depth of 1.7 inches with the same formula.

“For major land-disturbing activities, the SWRv is based upon the 90th percentile depth (1.2 inches). ... SWRv = P/12 × Rv × SA ... the WQTv ... is based upon the 95th percentile depth (1.7 inches).”
Appendix A, Pages A-1 to A-3

Peak flow calculation method(s)

Urban Hydrology for Small Watersheds TR-55, Storage-Indication Routing, NRCS TR-55 Curve Number Method, Modified CN Method, Rational Method

“Urban Hydrology for Small Watersheds TR-55 (TR-55) ... Storage-Indication Routing ... HEC-1, WinTR-55, TR-20, and SWMM Computer Models ... Rational Method (limited to sites under five acres)”
Appendix H, Page H-1

Required hydrologic/hydraulic software

HEC-1, WinTR-55, TR-20, SWMM

“HEC-1, WinTR-55, TR-20, and SWMM Computer Models”
Appendix H, Section H.4

Approved BMP categories

Green Roofs, Rainwater Harvesting, Simple Disconnection, Permeable Pavement Systems, Bioretention, Stormwater Filtering Systems, Stormwater Infiltration, Grass Channels, Dry Swales, Wet Swales, Stormwater Ponds, Stormwater Wetlands, Storage Practices, Proprietary Practices, Tree Planting, Tree Preservation

“Green Roofs ... Rainwater Harvesting ... Permeable Pavement Systems - Enhanced ... Bioretention - Standard ... Stormwater Infiltration ... Stormwater Ponds ... Stormwater Wetlands ... Tree Planting ... Tree Preservation”
Appendix A, Page A-6