Water sensitive design is being implemented via the Housing Accords and Special Housing Areas Act which implements the Proposed Auckland Unitary Plan (PAUP). Special Housing Areas have allowed Auckland Council to test planning provisions to encourage water sensitive design (WSD) in greenfields and brownfields scenarios.
Auckland Council’s Katja Huls and Andrew Chin presented a paper at the recent 2016 Water New Zealand Stormwater Conference in Nelson. 1. Huls & Chin – Commercial Benefits of Water Sensitive Design
They say their recent experience with implementing WSD is that it leads to a decentralised approach which provides strong commercial benefits which have been well received by the private development sector.
While WSD is intended to lead to good ecological, urban design and amenity outcomes, it also has less obvious benefits. Good WSD can do away with the need for large scale communal stormwater devices.
The retention and protection of streams avoids engineered flood management approaches because stream corridors can be designed to allow flood flows to be conveyed safely. Hydrology mitigation leads to stormwater management at a sub-catchment level with multiple devices higher in the catchment – a more decentralised approach.
This decentralised approach means that the implementation of stormwater infrastructure is not tied to negotiated agreements between private landowners or cumbersome public land acquisition processes.
It also leads to a shift in asset types, the use of smaller pipes and smaller devices which are significantly cheaper to build. Valuable land can be used more efficiently as smaller devices can be located within the road corridor, stream corridors and private lots.
Consequently there has been a shift in asset funding sources; from straight ratepayer investment to a mix of private, ratepayer and transport corridor investment. Decentralisation and the use of a treatment train approach is also less likely to result in significant device failure, providing a more resilient network.
Andrew Chin is chartered engineer and qualified planner, with experience in three water infrastructure approaching 18 years. He has worked professionally in the public and private sector both in New Zealand and the United Kingdom. He is currently the stormwater asset management team manager for Auckland Council.
Katja Huls is a qualified planner with 13 years’ experience in the planning profession, she has specialised in water for the majority of this time. She works for Auckland Council as a senior stormwater specialist providing stormwater input to structure and area planning processes for greenfields developments, and large scale brownfields development.