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 storms
Major 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 solution
One size fits all
Mimics natural hydrology
Dry up all the streams
Cost competitive to traditional
stormwater management
Free
Stormpond
Design
Volumes
Georgia Stormwater
Management Manual, Vol. 2
ARC 2001
Water Quality
Volume
Knoxville, TN Development Manual
Reducing Runoff Volume
6
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
Soils and vegetation – already present = free
 Inlet/Outlet control – direct inflow/overland flow = free
 Storage volume = predevelopment conditions
 Natural areas generally are counted as net zero
 Can they store, infiltrate, evapotranspirate
more than the design volume?
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
Reduce Pollutant
Loads
-Proper fertilizer and pesticide use
-Maintain vegetative cover
-BMP is a nutrient sink, not a nutrient source
(how green is green?)
-Stormwater contains nutrients
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 soilsedums 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
•
•
•
•
•
•
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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
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