ACC_Greenroofintro_May2009_merg

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Auckland City Green Roofs : 

Auckland City Green Roofs Mostly heavy ‘gardens’, often with foot-traffic (expensive structurally) Underground carparks Gun emplacements (disguise) Reservoirs (cooling water)

Why green roofs are being installed…currently in New Zealand : 

Why green roofs are being installed…currently in New Zealand landscape mitigation (blending structures into landscapes) mitigation of high site coverage (residential)

Why green roofs are being installed…in the East (Japan, Singapore) : 

Why green roofs are being installed…in the East (Japan, Singapore) Heat island reduction Urban gardening and overcoming nature deficit (health benefits) Enhance aesthetics in urban areas Noise mitigation (reduce noise getting in or out of a building)

Why green roofs are being installed…in Europe : 

Legislated for conservation of birds and insects found in ruderal sites (London, Basel - Zurich) Why green roofs are being installed…in Europe

Why green roofs are being installed…in Europe and North America : 

Why green roofs are being installed…in Europe and North America reduce flooding, combined sewer overflows Stormwater control is the Auckland driver

The Auckland Research programme… : 

The Auckland Research programme… Before promoting the use of green roofs for stormwater mitigation, ARC wanted to know: Effectiveness for stormwater control Local components

Lunchtime Learning Seminar : 

Lunchtime Learning Seminar Green Roofs: An Alternative Method for Stormwater Management 22 June 2009 Emily Voyde, PhD student

Why do we care about stormwater? : 

Why do we care about stormwater? Urbanisation in Auckland City Many impervious surfaces = More stormwater runoff Green roofs are one solution

Traditional stormwater management : 

Traditional stormwater management Structural controls Conveyance Gutters, curbs, pipes Hydraulically very efficient Stream erosion -> armouring Reactive mitigation Detention ponds Protect property Storm focus Detain peak flows

THERE IS A BETTER WAY : LID = SUDS = WSUD : 

THERE IS A BETTER WAY : LID = SUDS = WSUD

Low Impact Design (LID) : 

Low Impact Design (LID) “…is a design approach… that protects and incorporates natural site features into erosion and sediment control and stormwater management plans.” (ARC TP124) Source control (prevention) and infiltration Proactive mitigation near source Integrated site design Protect property AND habitat Mimic natural processes Stream protection and water quality focus requires treating small, frequent storms

LID – source control with small impervious footprints & stormwater treatment trains reducing contaminants, delaying & reducing stormwater volume discharged : 

LID – source control with small impervious footprints & stormwater treatment trains reducing contaminants, delaying & reducing stormwater volume discharged

Treatment trains in our backyards : 

Treatment trains in our backyards

Green roof components : 

Green roof components Vegetation (intercepts rainfall, releases moisture to the atmosphere) Substrate (plant growth, absorbs rainfall) Non-woven geotextile filter Drainage layer (drains to gutter system) Root Barrier & Waterproofing layers

Green Roofs in NZ : 

Green Roofs in NZ Substrates Plants

Installation Sept ‘06 : 

Installation Sept ‘06

Completion – Monitoring : 

Completion – Monitoring

UoA Green Roof: Stormwater Mitigation : 

UoA Green Roof: Stormwater Mitigation Overall retention efficiencies: 50 mm: 71% 70 mm: 73% Average peak flow reduction: 96% 63 events analysed (5 Sept 2008 to 21 Feb 2009) Depth: 0.2 mm to 59.0 mm Total rainfall depth = 374 mm Events causing runoff were =1.4 mm

23-24 Dec 2008: Volume Control : 

23-24 Dec 2008: Volume Control 50 mm: 52% retention efficiency 70 mm: 33% retention efficiency

23-24 Dec 2008: Peak Flow Control : 

23-24 Dec 2008: Peak Flow Control 50 mm: 79% peak flow reduction 70 mm: 80% peak flow reduction

Intl. Green Roofs: Volume Control : 

Intl. Green Roofs: Volume Control Field monitoring of full scale EGRs 50-68% retention of annual precipitation (Hutchinson et al. 2003; Mentens et al. 2006; Moran et al. 2005; Villarreal and Bengtsson 2005) Modelling studies 45-55% annual runoff retention (Berghage et al. 2007; US Environmental Protection Agency 2000)

Intl. Green Roofs: Peak Flow Control : 

Intl. Green Roofs: Peak Flow Control Portland green roof 80% peak flow reduction 15-month period (Hutchinson et al. 2003) North Carolina green roof 87% and 57% reduction 67 events v 13 events (Moran et al. 2005) Time lags for runoff Delays in onset of runoff Delays in time to peak Extended hydrograph duration (Carter and Rasmussen 2006; DeNardo et al. 2005; Liu 2003; Moran et al. 2005; VanWoert et al. 2005)

Where to next? : 

Where to next? Auckland City Today

Auckland City Green Roofs : 

Auckland City Green Roofs Can be the best in the world! Should be required on multi-storey buildings

Auckland City Green Roofs… : 

Auckland City Green Roofs… Make a public statement … Bus shelters ACC administration building Port buildings - views from cruise ships (Vancouver)

Slide 28: 

Any questions? Auckland Tomorrow.... ??