Stormwater framework for Kāpiti to manage more water, more development

Managing growth, and responding to climate change and Te Mana o te Wai in partnership with iwi are at the heart of a revised strategic framework for managing stormwater on the Kāpiti Coast.

Kāpiti Coast District Council and partners Te Ātiawa ki Whakarongotai, Ngā Hapū o Ōtaki and Ngāti Toa, supported by technical experts, have drafted a vision, values and outcomes for managing stormwater in the district, which will replace the existing strategy adopted in 2008.

“A lot has changed at a national, regional, and district level since the current strategy was developed including more frequent and severe rainfall events, increased growth, and new standards that put a holistic focus on water quality rather than an approach that simply manages quantity,” says Rita O’Brien, Stormwater & Coastal Engineer for Council.

“The impacts of managing high volumes of stormwater are relatively straight forward, but managing the quality of the water is far more complex. How we manage land use is a core part of the solution.

“There is also a complicated web of legislation and regulators, all with varying requirements and our framework aims to pull it all together. A large part of this is embedding the national concept of Te Mana o te Wai. This is about integrating the holistic health and wellbeing of water into managing land use to improve the health of our water bodies and protect our community from flood hazards.

“This is assisted by Greater Wellington Regional Council’s whaitua (‘catchment’) committees that are responsible for setting water quality and quantity targets in order to uphold what communities value about freshwater bodies in their area.”

The Stormwater Steering Group, which also includes Regional Council representatives, has been meeting almost monthly since late 2020, to identify issues and information gaps, and potential solutions.

The Steering Group has proposed a vision for a future stormwater management system where:

• water is given space to flow from the hills to the sea
• the health of our water bodies is restored and protected
• communities are thoughtfully planned to be protected from flooding and resilient to climate change impacts, and
• Council partners with tāngata whenua to give expression to Te Mana o Te Wai to improve the mauri (holistic health) of our water bodies and protect us from floods.

“Essentially, we need to find a way to live better with more. More water. More urban development. More growth. Kāpiti has 210km of stormwater pipes and a vast network of open channels and streams, with many likely not to cope with flows from a 1-in-10-year rainfall event,” says Ms O’Brien.

“Increasing the size of the pipes or the network is not always an option due to both physical constraints – there simply may not be room for bigger pipes - and because the upgrade costs may outweigh the benefits.

“While Council has always looked beyond the traditional ‘collect, convey, discharge’ approach, a greater understanding of the role of land use in urban stormwater quality management is needed. 

“A more cost-effective alternative is storing rainfall close to where it lands, re-using it or slowly releasing it back into the stormwater network, and retrofitting or requiring new developments to store and treat stormwater on site. Where there’s space, a good option is creating ‘treatment’ facilities that imitate natural landforms and processes, like stormwater wetlands.”

Ahead of adoption, Council is seeking community feedback on the draft vision, values and outcomes proposed by the Steering Group.

For more on stormwater management and to have your say, visit Stormwater Management Framework.