Evaluating Stormwater BMPs Frank Henning Region IV Land Grant Universities Liaison Insert Unit # and Title

What Low Impact Development Is and Is Not LID Is:LID Is Not: Volume control for small stormsMajor flood control Better stormwater management for new & existing development Anti-development Requires complementary approaches for large storms A stand-alone solution for all wet weather management Scale site specific solutionOne size fits all Mimics natural hydrologyDry up all the streams Cost competitive to traditional stormwater management Free

Georgia Stormwater Management Manual, Vol. 2 ARC 2001 Stormpond Design Volumes

Water Quality

Volume Knoxville, TN Development Manual

6 Reducing Runoff Volume

Flow Volume

Green Infrastructure/LID – Preserves natural environments – Retains stormwater volume for infiltration, evapotranspiration, or use – Removes the volume from the stream – Mimics natural hydrology, often enhances groundwater recharge and base flow – Removes pollutant load associated with the volume retained – Does not transfer pollution to ground water – May need additional storage to address stream protection and flood prevention requirements

Natural Area Preservation  Storage volume = predevelopment conditions  Natural areas generally are counted as net zero  Can they store, infiltrate, evapotranspirate more than the design volume?  Soils and vegetation – already present = free  Inlet/Outlet control – direct inflow/overland flow = free Wetlands Franklin, TN Maryville TN Buffers Maryville TN Springhead

Soil Enhancement Program Cost – usually minimal or low Storage – enhance void space and infiltration rate of soil Soil – amended soil and native soil infiltration rate Vegetation – selection based on site Inlet/Outlet – direct inflow, overland or directed

Vegetative Cover

-Proper fertilizer and pesticide use -Maintain vegetative cover -BMP is a nutrient sink, not a nutrient source (how green is green?) -Stormwater contains nutrients Reduce Pollutant Loads

Disconnection Programs Storage – based voids, and infiltration rate of soil, impervious area disconnected (capture area) Soils – amended or uncompacted native soil Vegetation – selection based on the site Inlet/Outlet – downspouts, sheet flow over vegetated areas to swales, sewers, waterbodies

Tree Canopy Programs Storage volume - based on pool volume, void space of amended soil, native soil infiltration rate, evapotranspiration rate, capture area Soil – structural or amended for storage/pollutant uptake Vegetation - trees for largest amount of evapotranspiration, other benefits Inlet /Outlet Controls – must provide!

Rainwater Harvesting & Use Storage volume – Water Use – irrigation or other use Soils - infiltration Vegetation – evapotranspiration Inlet/Outlet - must be provided Outlet protection – reduce erosion

Green Parking – Permeable Pavement

Green Roofs Storage – soil depth/voids Soils – amended, structured Vegetation – intensive (shallow soil- sedums or drought tolerant species) or extensive (deep soil-small tree, shrubs) Inlet /Outlet – direct capture/roof drains Structural – must perform analysis

Raingardens/Bioretention Storage Volume – based on pool design, amended soil void space, capture area Soils - native soils are removed and replaced with amended soil Vegetation - herbaceous (low evapotranspiration) Inlet/ Outlet controls - direct inflow and provide for bypassing larger events

Volume Comparison Burnsville, MN Neighborhood Rain Garden Study Barr Engineering

Other GI/LID Benefits Air quality improvement Community beautification Energy savings Health benefits Heat island reduction Property value improvement Recreation and wildlife

Acknowledgements Module contributors: Material for this module was adapted from presentations and publications by Region IV EPA Watershed Protection Division Module editors: [Insert names and affiliations here for at least 2 peer-reviewers] Southern Region Landscape Team: Amy Shober (UF/IFAS); Lucy Bradley (NCSU); Eve Brantley (Auburn); Wendi Hartup (NCSU); Barbara Fair (NCSU); Frank Henning (USEPA/UGA); Esen Momol (UF/IFAS); Kerry Smith (Auburn); Dotty Woodson (Texas Agrilife); Sheryl Wells (UGA) Funding for this module provided by: USDA-NIFA National Water Program, Southern Regional Water Program special project funds Graphic design: Emily Eubanks - UF/IFAS Center for Landscape Conservation and Ecology; Amy L. Shober – UF/IFAS Gulf Coast Research and Education Center 21