Low Impact Development Handbook for the State of Alabama Alabama Department of Environmental Management Alabama Cooperative Extension System Auburn University Low Impact Development Handbook Alabama Department of Environmental Management in cooperation with the Alabama Cooperative Extension System and Auburn University Contributing Authors: Graphic Design: Katie L. Dylewski Domini V.J. Cunningham Jessica T. R. Brown Taylor French Charlene M. LeBleu Oliver Preus Dr. Eve F. Brantley Appreciation is extended to the reviewers who provided expertise and guidance: Barry Fagan, Earl Norton, Perry Oakes, Missy Middlebrooks, Patti Hurley, Norm Blakey, and Randy Shaneyfelt. Thanks also to those who provided guidance on stormwater control measures and vegetation considerations: Dr. Mark Dougherty, Ryan Winston, Dr. Amy Wright, Dr. Julie Price, Kerry Smith, Dr. Bob Pitt, Vernon ‘Chip’ Crockett, Jeff Kitchens, and Rhonda Britton. This project was partially funded by the Alabama Department of Environmental Management through a Clean Water Act Section 319(h) nonpoint source grant provided by the U.S. Environmental Protection Agency - Region 4 to support the Alabama Nonpoint Source Management Program, the Alabama Coastal Nonpoint Pollution Control Program under the Coastal Zone Act Reauthorization Amendments of 1990 (CZARA), and implementation of CWA Section 319 and CWA Section 6217 Coastal NPS management actions and measures. How to use this Handbook ...........................................................................................1 Overview .............................................................................................................................. 5 Site Selection ..................................................................................................................... 9 Community Planning ................................................................................................... 19 Practices ............................................................................................................................ 24 Bioretention ......................................................................................................................25 Constructed Stormwater Wetlands .................................................................................47 Permeable Pavement .......................................................................................................73 Grassed Swales, Infi ltration Swales, and Wet Swales ...................................................87 Level Spreaders and Grassed Filter Strips ...................................................................107 Rainwater Harvesting .....................................................................................................118 Green Roofs ................................................................................................................... 125 Riparian Buffers .............................................................................................................134 Retrofi ts / Alternatives ........................................................................................... 144 Rain Gardens ...................................................................................................................145 Curb Cuts ..........................................................................................................................165 Disconnected Downspouts .............................................................................................169 Appendices .................................................................................................................... 174 Appendix A: Stormwater Hydrology ................................................................................175 Appendix B: Community Planning Resources .............................................................. 184 Appendix C: Maintenance .............................................................................................. 205 Appendix D: Vegetation and Alabama Native Plant List ...............................................212 Acronyms ADEM ..................................................................................Alabama Department of Environmental Management ADPH ...........................................................................................................Alabama Department of Public Health ALDOT ...................................................................................................... Alabama Department of Transportation ALNHP ............................................................................................................. Alabama Natural Heritage Program ASTM ................................................................................................. American Society for Testing and Materials BRC ................................................................................................................................................. Bioretention Cell CC .................................................................................................................................................................Curb Cut CGP ......................................................................................................................................... Concrete Grid Pavers cfs .......................................................................................................................................... Cubic feet per second CN ........................................................................................................................................................Curve number CPESC ............................................................................... Certifi ed Erosion and Sediment Control Professional CRF ............................................................................................................................. Controlled Release Fertilizer CWA ..................................................................................................................................................Clean Water Act CSW .................................................................................................................... Constructed Stormwater Wetland DD ....................................................................................................................................Disconnected Downspout DA ........................................................................................................................................................ Drainage area DIY ....................................................................................................................................................... Do-It-Yourself FAC ........................................................................................................................................................... Facultative FACW ................................................................................................................................................. Facultative wet FEMA .....................................................................................................Federal Emergency Management Agency fps .................................................................................................................................................... Feet per second GFS .............................................................................................................................................Grassed Filter Strip GI ............................................................................................................................................... Green Infrastructure gpm .............................................................................................................................................. gallons per minute GR ............................................................................................................................................................ Green Roof GS ...................................................................................................................................................... Grassed Swale HOA ................................................................................................................................Home Owner’s Association HSG ........................................................................................................................................Hydrologic Soil Group IA ...................................................................................................................................................... Impervious area IBC ................................................................................................................................ International Building Code IDF curve ........................................................................................................ Intensity-Duration-Frequency curve IS ..................................................................................................................................................... Infi ltration Swale IWS ..........................................................................................................................................Internal water storage LA ..............................................................................................................................................Landscape