ALiDP - City of Edmonton Fall Training Event, November 25, 2013

Slowing Down On Green Roofs Presented on behalf of Greater Edmonton Green Roof Consortium

Wilma Leung CEng, MICE, LEED-AP Email: wleung@williamsengineering.com

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Slowing Down On Green Roofs

Reduce Peak Flow

Delay Peak Flow

Reduce Total Runoff

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Slowing Down On Green Roofs

Source: www.ec.gc. ca

Or With Green Roof

Delay & Reduce Peak Flow

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Slowing Down On Green Roofs

Reduce Total Runoff

Source: environmentalsciencesociety. org

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Slowing Down On

Blue Roof

Source: www.perviouspavement. org

Source: Alumasc

Roof D

ischargeD

ownstream

Storm

Sew

er or

Com

bined Sew

er

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Slowing Down On

Blue Roof

Source: www.perviouspavement. org

DETENTION AND EVAPORATION OFFERED BY BLUE ROOFS

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Slowing Down On Green Roofs

Green Roof: Types

Intensive : > 8”, $$$$$

Extensive: 2” – 8”, $$, 17 – 50 lbs/sfBuilt-up or Tray Systems

Source: www.wbdg. org

Source: www.salinitymanagement. org

INTENSIVE SEMI-INTENSIVE EXTENSIVE

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Slowing Down On Green Roofs Green Roof: detention, evaporation, infiltration, percolation, evapotranspiration, . . . Water designed to flow through medium vertically before laterally along drainage layer.

Source: www.greenroofplan. com Source: environmentalsciencesociety. org

VEGETATION

GROWING MEDIUM

FILTER / ROOT BARRIER

DRAINAGE

INSULATION

WATER-PROOFING

STRUCTURE

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Slowing Down On Green Roofs

Green Roof: detention, evaporation, infiltration, percolation, evapotranspiration, . . . Water designed to flow through medium vertically before laterally along drainage layer.

Special design considerations needed when designing a pitched green roof to preserve hydrological benefits of green roof.

Source: environmentalsciencesociety. orgSource: www.hydrotechusa. com

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Slowing Down On Green Roofs Green Roof: detention, evaporation, infiltration, percolation, evapotranspiration. . .

Source: www.princeton. edu

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Slowing Down On Green Roofs Green Roof: detention, evaporation, infiltration, percolation, evapotranspiration. . .

Source: www.emeraldinsight. com

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Slowing Down On Green Roofs Green Roof: detention, evaporation, infiltration, percolation, evapotranspiration, retention

Source: Paul MJ & Meyer JL, and USEPA

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Slowing Down On Green Roofs Green Roof: detention, evaporation, infiltration, percolation, evapotranspiration, retention

Source:environmentalsciencesociety. org

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Slowing Down On Green Roofs

Source:Hydrological performance of extensive green roofs in New York City: observations and multi-year modeling ofthree full-scale systems. T B Carson et al 2013 Environ. Res. Lett. 8 024036 doi:10.1088/1748-9326/8/2/024036

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Slowing Down On Green Roofs

Source: enr.construction. com

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Slowing Down On Green Roofs

Source: enr.construction. com

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Slowing Down On Green Roofs

Source: www.emeraldinsight. com

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Slowing Down On Green Roofs

Source: prairieecosystems.pbworks. com

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Slowing Down On Green Roofs Green Roofs: with cisterns or harvesting

Source: www.ce.t.kyoto-u.ac. jp

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Slowing Down On Green Roofs

Source: nusdeltares. org

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Slowing Down On Green Roofs Green Roof: Effects of Rain Duration & Intensities

Source: uregina. ca (modified)

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Slowing Down On Green Roofs

Green Roof: Runoff Quality & Pollution Control

Source: www.lid-stormwater. net

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Slowing Down On Green Roofs Selection of Green Roof Components:

Drainage

•Drainage Layer• Use of Lightweight Aggregate?• Plastic Drainage Sheets ?• Closed-cell polystyrene trays ?

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Slowing Down On Green Roofs Selection of Green Roof Components:

Drainage

• Drainage Layer• Use of Lightweight Aggregate?• Plastic Drainage Sheets ?• Closed-cell polystyrene trays ?

•Low Transmissivity Drainage Fiber Mat

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Slowing Down On Green Roofs Selection of Green Roof Components:

Drainage

• Drainage Layer• Use of Lightweight Aggregate?• Plastic Drainage Sheets ?• Closed-cell polystyrene trays ?

• Low Transmissivity Drainage Fiber Mat•Slope to Drain • Ability to Remove Excess Stormwater without Causing Erosion

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Slowing Down On Green Roofs Selection of Green Roof Components:

Drainage

• Drainage Layer• Use of Lightweight Aggregate?• Plastic Drainage Sheets ?• Closed-cell polystyrene trays ?

•Low Transmissivity Drainage Fiber Mat•Slope to Drain • Ability to Remove Excess Stormwater without Causing Erosion• Maintain Aerated Conditions in the Growing Medium

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Slowing Down On Green Roofs Selection of Green Roof Components:

Soil Saturation & Plant Available Water

Source: www.bae.ncsu.edu

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Slowing Down On Green Roofs Selection of Green Roof Components:

Growing Media for Stormwater Benefits

• Media Thickness: 2”, 3”, 4”, 4”-8”, 8” – 48”

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Slowing Down On Green Roofs Selection of Green Roof Components:

Growing Media for Stormwater Benefits

• Media Thickness: 2”, 3”, 4”, 4”-8”, 8” – 48”

• Sponge-like Water Holding Capacity

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Slowing Down On Green Roofs Selection of Green Roof Components:

Growing Media for Stormwater Benefits

• Media Thickness: 2”, 3”, 4”, 4”-8”, 8” – 48”

• Sponge-like Water Holding Capacity

• Saturated Weight of Growing Media

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Slowing Down On Green Roofs

Selecting Plants for Stormwater Benefits

• Drought, wind and freeze-thaw • Prairie species• Avoid large drifts of single species• Water absorption• Requires very little or no irrigation • Requires very little or no fertilizer

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Slowing Down On Green Roofs

Selecting Plants: A Comparison

Shortgrass

Stormwater Retention

Transpirative Cooling

Pollutant Removal

Biodiversity

Sedum

Light Weight Components

Low Maintenance

Drought Resistant

Source: http://www.daniels.utoronto.ca

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Slowing Down On Green Roofs

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Slowing Down On Green Roofs

Impact of Green Roofs on Urban Catchment

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Slowing Down On Green Roofs

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Slowing Down On Green Roofs

Design Tools and Guidelines ?Listen to Bert tomorrow !

ALiDP - City of Edmonton Fall Training Event, November 25, 2013

Slowing Down On Green Roofs Presented on behalf of Greater Edmonton Green Roof Consortium

Wilma Leung CEng, MICE, LEED-AP Email: wleung@williamsengineering.com

THANK YOU