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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.

    Clear Creek Solutions, Inc.
   Presentation
        Introduction
    Permeable Pavement
       Rain Gardens
Impervious Runoff Dispersion
        Green Roofs
   Rainwater Harvesting
  Watershed Reforestation
         Summary
           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.
             Introduction

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.
                             Summary

                                             Change in       Change in
LID Options:                  Soil         Surface Water    Groundwater
                                            (ac-ft/ac/yr)    (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.

                                 Change in       Change in
LID Option:        Soil        Surface Water    Groundwater
                                (ac-ft/ac/yr)    (ac-ft/ac/yr)
Permeable
              Till / Outwash       -2.5             +1.7
  Pavement
 Permeable Pavement Flow Paths
        Evaporation from
                                         Rain on
           pavement
                                        pavement




Surface Runoff       Infiltration through pavement

                 Infiltration to gravel subgrade



  Underdrain Flow          Infiltration to
                             native soil
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:
     1. Evaporation.
     2. Transpiration.
     3. Infiltration.
                              Change in       Change in
LID Option:         Soil    Surface Water    Groundwater
                             (ac-ft/ac/yr)    (ac-ft/ac/yr)
Roof Runoff
                    Till        -0.4             +0.3
  Dispersion
Roof Runoff
                  Outwash       -2.3             +2.2
  Dispersion
 Roof Runoff Dispersion Flow Paths




                                  Impervious Roof
                                     Surface


  Surface Runoff
                             Pervious Surface

      Interflow
                                 Infiltration to
                                  Native Soil
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.
                           Change in       Change in
LID Option:     Soil     Surface Water    Groundwater
                          (ac-ft/ac/yr)    (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.
                            Change in       Change in
LID Option:       Soil    Surface Water    Groundwater
                           (ac-ft/ac/yr)    (ac-ft/ac/yr)
Rain Gardens      Till        -0.5             +0.4
Rain Gardens    Outwash       -1.4             +1.0
WWHM Rain Garden Modeling

Downstream control structure:




  Water infiltrates into the soil before runoff.
       Rain Garden Flow Paths

                                               Inflow to
                                              Bioretention
                                                 Facility


Weir Flow

  Vertical     Infiltration to Amended Soil
Orifice Flow

  Underdrain Flow      Infiltration to
                        Native Soil
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.

                         Change in       Change in
LID Option:     Soil   Surface Water    Groundwater
                        (ac-ft/ac/yr)    (ac-ft/ac/yr)
Rainwater
                N/A        -0.04            +0.0
  Harvesting
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.
Watershed Reforestation
Reforestation Reduces Runoff
Volume:

     1. Evaporation.
     2. Transpiration.
     3. Infiltration into soil.
                              Change in       Change in
LID Option:         Soil    Surface Water    Groundwater
                             (ac-ft/ac/yr)    (ac-ft/ac/yr)
Watershed
                    Till        -0.7             +0.3
  Reforestation
Watershed
                  Outwash      -0.006            -0.4
  Reforestation
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

                                             Change in       Change in
LID Options:                  Soil         Surface Water    Groundwater
                                            (ac-ft/ac/yr)    (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.
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 425.892.6454
beyerlein@clearcreeksolutions.com

				
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