psgb ecosystem conference the effectiveness of lids in reducing stormwater runoff february 9, 2009
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PSGB Ecosystem Conference The Effectiveness of LIDs in Reducing Stormwater Runoff February 9, 2009. Doug Beyerlein, P.E. Clear Creek Solutions, Inc. This presentation was originally given at the Puget Sound Georgia Basin Conference in Seattle, WA, in February 2009 by . Doug Beyerlein, P.E. - PowerPoint PPT PresentationTRANSCRIPT
PSGB Ecosystem PSGB Ecosystem ConferenceConference
The Effectiveness of LIDs in The Effectiveness of LIDs in Reducing Stormwater RunoffReducing Stormwater Runoff
February 9, 2009February 9, 2009Doug Beyerlein, P.E. Doug Beyerlein, P.E.
Clear Creek Solutions, Inc.Clear Creek Solutions, Inc.
This presentation was originally given at the
Puget Sound Georgia Basin Conference in Seattle, WA,
in February 2009by
Doug Beyerlein, P.E. Doug Beyerlein, P.E.
Clear Creek Solutions, Inc.Clear Creek Solutions, Inc.
PresentationPresentation IntroductionIntroduction
Permeable PavementPermeable Pavement
Rain GardensRain Gardens
Impervious Runoff Dispersion Impervious Runoff Dispersion
Green RoofsGreen Roofs
Rainwater HarvestingRainwater Harvesting
Watershed Reforestation Watershed Reforestation
SummarySummary
Introduction
There is nothing magical about LIDs.Stormwater must go somewhere.Stormwater must either:1. Infiltrate into the soil.2. Evaporate/transpire into the atmosphere.3. Runoff.
Introduction
Key considerations in LID effectiveness in the PSGB region:
1. Type of soil: till or outwash.2. Type of vegetation: forest, pasture, urban.
Introduction
LID hydrologic modeling requires continuous simulation: WWHM (HSPF)Continuous simulation hydrology models the entire hydrologic cycle for multiple years.
WWHM: Western Washington Hydrology Model
• Developed for the State of Washington Department of Ecology.• Has the ability to model a full range of LID facilities and practices.
Introduction
Summary
LID Options: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Permeable Pavement Till / Outwash -2.5 +1.7
Roof Runoff Dispersion Till -0.4 +0.3
Roof Runoff Dispersion Outwash -2.3 +2.2
Green Roofs N/A -0.7 +0.0
Rain Gardens Till -0.5 +0.4
Rain Gardens Outwash -1.4 +1.0
Rainwater Harvesting N/A -0.04 +0.0
Watershed Reforestation Till -0.7 +0.3
Watershed Reforestation Outwash -0.006 -0.4
Permeable Pavement
Permeable Pavement Reduces Runoff Volume:
1. Evaporation.2. Infiltration to native soil.
LID Option: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Permeable Pavement Till / Outwash -2.5 +1.7
Permeable Pavement Flow Paths
Infiltration to native soil
Surface Runoff
Rain on pavement
Infiltration to gravel subgrade
Underdrain Flow
Infiltration through pavement
Evaporation from pavement
Permeable Pavement
Reasons why permeable pavement is a good LID option in PSGB region:
1. Ratio of drainage area to infiltration facility area is 1 to 1.
2. Western Washington rainfall volumes and intensities are relatively low.
3. Subsurface storage provides water for long-term slow infiltration and evaporation.
Roof Runoff Dispersion
Dispersion of impervious roof runoff on adjacent pervious lawn allowing some water to infiltrate before becoming stormwater runoff.
Roof runoff dispersion reduces runoff volume by slowing the runoff velocity and allowing:
1. Evaporation from adjacent pervious land.
2. Transpiration from adjacent pervious land.
3. Infiltration on adjacent pervious land.
Roof runoff dispersion reduces runoff volume by slowing the runoff velocity and allowing:
LID Option: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Roof Runoff Dispersion Till -0.4 +0.3
Roof Runoff Dispersion Outwash -2.3 +2.2
1. Evaporation.2. Transpiration.3. Infiltration.
Roof Runoff Dispersion Flow Paths
Infiltration to Native Soil
Impervious Roof Surface
Pervious Surface
Surface Runoff
Interflow
Infiltration to native soil is dependent on native soil characteristics.
Roof Runoff Dispersion
Reasons why impervious runoff dispersion is a good LID option in PSGB region:
1. Turns impervious runoff into pervious runoff.
2. Works best with outwash soils; less benefit with till/poor draining soils
3. Soil moisture storage provides water for infiltration and evapotranspiration.
Green Roofs
Green Roofs Reduce Runoff Volume:
1. Evaporation.2. Transpiration.
LID Option: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Green Roofs N/A -0.7 +0.0
Green Roof Flow Paths
Green Roofs
Reasons why green roofs are a good LID option in PSGB region:
1. Can be used in highly developed urban areas.
2. Soil moisture storage provides water for evapotranspiration.
Rain Gardens
Includes planter boxes
Rain Gardens Reduce Runoff Volume:
1. Evaporation.2. Transpiration.3. Infiltration to native soil.
LID Option: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Rain Gardens Till -0.5 +0.4
Rain Gardens Outwash -1.4 +1.0
WWHM Rain Garden ModelingDownstream control structure:
Water infiltrates into the soil before runoff.
Rain Garden Flow Paths
Infiltration to Native Soil
Weir Flow
Inflow to Bioretention
Facility
Infiltration to Amended Soil
Underdrain Flow
Vertical Orifice Flow
Rain Gardens
Reasons why rain gardens are a good LID option in PSGB region:
1. Regardless of volume reduction there are good water quality benefits.
2. Works best with outwash soils; less benefit with till/poor draining soils
3. Soil moisture storage provides water for long-term slow infiltration and evapotranspiration.
Rainwater Harvesting
Rainwater Harvesting Reduces Runoff Volume:
1. Storage for later application and evapotranspiration.
LID Option: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Rainwater Harvesting N/A -0.04 +0.0
Rainwater Harvesting
Reasons why rainwater harvesting is a good LID option in PSGB region:
1. Can be used in highly developed urban areas.
2. Can reduce municipal water supply demand for irrigation.
Reforestation Reduces Runoff Volume:
1. Evaporation.2. Transpiration.3. Infiltration into soil.
LID Option: SoilChange in
Surface Water (ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Watershed Reforestation Till -0.7 +0.3
Watershed Reforestation Outwash -0.006 -0.4
Reforestation
Reasons why reforestation is a good LID option in PSGB region:
1. Works best with till soils; less benefit with outwash soils.
2. Soil moisture storage provides water for long-term slow infiltration and evapotranspiration.
3. Provides wildlife habitat.4. Reduces carbon footprint.
Summary
LID Options: SoilChange in
Surface Water(ac-ft/ac/yr)
Change in Groundwater (ac-ft/ac/yr)
Permeable Pavement Till / Outwash -2.5 +1.7
Roof Runoff Dispersion Till -0.4 +0.3
Roof Runoff Dispersion Outwash -2.3 +2.2
Green Roofs N/A -0.7 +0.0
Rain Gardens Till -0.5 +0.4
Rain Gardens Outwash -1.4 +1.0
Rainwater Harvesting N/A -0.04 +0.0
Watershed Reforestation Till -0.7 +0.3
Watershed Reforestation Outwash -0.006 -0.4
Summary
In PSGB region:
1. Permeable pavement is the most effective LID to reduce stormwater runoff, regardless of soil type.
2. Roof runoff dispersion into outwash soil is the most effective LID to increase groundwater recharge.
AcknowledgementsSeattle Public Utilities provided much of the funding for the modeling of green roofs and rain gardens.
Taylor Associates of Seattle provided info and photos of Seattle green roofs.
The City of Portland, Oregon, Bureau of Environmental Services (BES) provided the Hamilton green roof monitoring data.
