Water Sensitive Urban Design (WSUD) in New Zealand

WATER SENSITIVE URBAN DESIGN WSUD IN NEW ZEALAND • • • • •

The definition/importance of WSUD The principles and objectives The main approaches of WSUD Other environmental services achieved by WSUD Case studies of WSUD (Christchurch, Wellington and Auckland)

WATER SENSITIVE URBAN DESIGN WHAT IS WUSD ?

WSUD is an approach to water management in towns and cities that addresses both water quantity and water quality issues. WSUD draws upon the processes of natural systems and adapts these to suit urban environments. It integrates the processes inherent in water systems with the ‘built environment’ – buildings, infrastructure and landscapes.

The urban water system includes potable water, wastewater and stormwater. This booklet focuses, for now, primarily on stormwater, but in doing so will have positive effects on potable water demand and issues with unintended wastewater discharges.

A stormwater system allows the passage of runoff to avoid nuisance flooding and consequential damage to public and private property. A WSUD system must support this vital function.

The overarching objectives of WSUD are: 1. Protect or enhance the environmental, social and economic values of downstream environments 2. Reduce the frequency, duration and volume of stormwater runoff to mitigate the risks of nuisance flooding and moderate post-development flows to waterways 3. Reduce demand on potable water supply 4. Improve amenity in the urban environment.

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A Guide For WSUD Stormwater Management In Wellington, Wellington City Council

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WSUD APPROACHES LOW-DENSITY RESIDENTIAL DEVELOPMENT

ISSUES Demand/need for landscape amenity Reliance on mains water Impervious pavements increase runoff.

PERMEABLE PAVEMENT

GOAL Collect, detain and reuse stormwater on site to reduce discharge into stormwater network.

VEGETATION COVER

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VEGETATIVE COVER

WSUD APPROACHES MEDIUM OR HIGH-DENSITY DEVELOPMENT

ISSUES High site coverage (imperviousness) increases runoff Range of demands and uses of limited open space.

GREEN WALL

GOAL Collect, detain and treat stormwater to improve quality and reduce discharge from site. Integrate WSUD measures to create multifunctional architecture and open space.

RAIN GARDEN

GREEN ROOF

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WSUD APPROACHES INDUSTRIAL DEVELOPMENT

ISSUES High site coverage increases runoff Often increased contaminant loadings due to nature of vehicle movements Inherent risk associated with on-site hazardous substances.

GOAL Collect, detain and treat stormwater to improve quality and reduce discharge from site. Use WSUD measures to mitigate effects that may be associated with commercial and industrial activities.

SUBSURFACE RAIN TANK

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STREET TREES

BIO-RETENTION SYSTEM

WSUD APPROACHES STREETS, PRIVATE WAYS AND CAR PARKS

ISSUES Contamination accumulation on surfaces and conveyance by stormwater runoff Competing demand for space (at and below grade) for amenity, movement and provision of services GOAL The integration of collection, detention, treatment and infiltration of stormwater within road reserves, private ways and car parks, prior to discharge into the conventional stormwater network.

RAIN GARDEN

INFILTRATION TRENCH

DETENTION POND

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WSUD APPROACHES PARKS AND GARDENS

ISSUES Recreational needs of the community may restrict where and to what extent WSUD measures occur. New parks should be planned to accommodate multiple uses.

GOAL Design parks/gardens to provide detention and retention to mitigate adverse effects of stormwater runoff on downstream system, while balancing the recreational needs of the community.

RAIN GARDEN

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CONSTRUCTED WETLANDS

VEGETATED SWALE

OTHER ENVIRONMENTAL SERVICES

ECOSYSTEM RESTORATION

URBAN GREENING

SOCIAL AMENITY

HABITAT AND BIODIVERSITY

AESTHETIC VALUE

ECOLOGY EDUCATION 8

WELLINGTON WSUD CASE STUDY WAITANGI PARK

Waitangi Park is one of the best practices in New Zealand that combines water sensitive urban design with high-level recreational uses.

The stormwater management system consists of several crutial steps. Stormwater from the culvert is ‘daylighted’ via a pumping system which is linked to level and salinity sensors to exclude seawater at high tide. Then water enters a sub-surface wetland designed to reduce turbidity in the stormwater to levels suitable for UV disinfection. Any grease, solids and silts are removed here. Flows within the Waitangi Stream wetland are treated through filtration, absorption and biological/chemical transformation before entering Wellington Harbour. Finally, treated stormwater from the wetland is used to irrigate the park and the neighbouring grounds of Te Papa. water quality

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http://www.waal.co.nz

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WELLINGTON WSUD CASE STUDY COBBLESTONE PARK

Located just outside of Victoria University’s architecture and design school in Wellington, Cobblestone Park is recently revised for dynamic public uses and ecological functions.

Besides the children playground, half-size basketball field and the lawn terrace with public seatings, the green spaces are divided by the axis pathway and are turned into terraced rain gardens that filter the site-generated storm-water runoff both from the street and the roof of the surrounding buildings; reeds like wind-swept hair that are a softening counterpoint to the angular geometry of concrete-framed terraces. The park is a great example of integrating simple interventions in a small-scale site for WSUD. water quality

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http://www.waal.co.nz https://architecturenow.co.nz/articles/cobblestone-park/#img=1

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AUCKLAND WSUD CASE STUDY SILO PARK AND JELLICOE STREET

Silo Park is situated in the Wynyard Quarter – an area of exciting revitalization in the heart of Auckland’s waterfront. Being as a significant part of Auckland’s industrial history, the park itself is now a popular inner-city oasis for the community and the visitors.

The linear shape constructed wetlands in Silo Park, as well as the rain gardens/bioswales along the Jellicoe Street, are designed to collect and treat the run-off on site before it is discharged into the bay, which help to improve the water quality by reducing the contaminants in the stormwater. water quality

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https://www.silopark.co.nz

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AUCKLAND WSUD CASE STUDY BARRY CURTIS PARK

Barry Curtis Park is a giant piece of public infrastructure embedded into land with a town centre growing slowly around it.

Stormwater management is integrated into the site design for collecting, filtrating and storing. The streams were restored for native ecosystem. The ponds and wetlands, were created out of low-lying areas. They contrast with the earthworks and other designed pieces of infrastructure and generate both a strong design aesthetic, through their thick green margins, and a means for people to explore right down beside, and in some instances, right over, the water. water quality and quantity

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http://isthmus.co.nz

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CHRISTCHURCH WSUD CASE STUDY ADDINGTON

Addington is one of the Christchurch’s oldest neighbourhoods. In the Streetscape Enhacement Project, the curb and channel renewal seeks to mitigate the effects of flooding, improve stormwater quality and improve amenity values.

Several approaches have been applied along the streets as well as in the open spaces.

First flush ponds can hold polluted water for a short amount of time before pollutants settle and the water drains away. Differents types of rain gardens are constructed for both heavy rainfalls and low intensity rain fall events. And vegetated swales are designed to slow stormwater run-off and improve water quality as well as bringing aesthetically pleasing to the community.

During the 2010/2011 Christchurch earthquakes, these green infrastructures survived in the desaster due to its resiliency and are still performing well until now. water quantity natural disturbances 17

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REFERRENCES 1. GD04 Water Sensitive Design for Stormwater, Auckland Council 2. Water Sensitive Urban Design A Guide For WSUD Stormwater Management In Wellington, Wellington City Council 3. http://isthmus.co.nz 4. http://www.waal.co.nz 5. https://www.silopark.co.nz 6. http://www.boffamiskell.co.nz 7. https://architecturenow.co.nz/articles/cobblestone-park/#img=1

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WATER SENSITIVE URBAN DESIGN WSUD IN NEW ZEALAND • • • • •

The definition/importance of WSUD The principles and objectives The main approaches of WSUD Other environmental services achieved by WSUD Case studies of WSUD (Christchurch, Wellington and Auckland)