PSGB Ecosystem Conference The Effectiveness of LIDs in Reducing Stormwater Runoff February 9, 2009...

PSGB Ecosystem PSGB Ecosystem ConferenceConference

The Effectiveness of LIDs in The Effectiveness of LIDs in Reducing Stormwater RunoffReducing Stormwater Runoff

February 9, 2009February 9, 2009

Doug 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



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:





Till -0.4 +0.3


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.


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.





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.






WWHM Rain Garden Modeling

Downstream 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.





N/A -0.04 +0.0


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.

Watershed Reforestation

Reforestation Reduces Runoff Volume:

1. Evaporation.2. Transpiration.3. Infiltration into soil.





Till -0.7 +0.3


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)


Permeable Pavement Till / Outwash -2.5 +1.7

Roof Runoff Dispersion Till -0.4 +0.3

Roof Runoff Dispersion Outwash -2.3 +2.2




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.

Acknowledgements

Seattle 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.

Questions?

Contact:

Doug Beyerlein [email protected]

PSGB Ecosystem Conference The Effectiveness of LIDs in Reducing Stormwater Runoff February 9, 2009...

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