Te Awarua-o-Porirua (Porirua Harbour) was once a thriving tidal estuary and home to marine and migratory fish, shellfish, birds and plants. Land uplift from earthquakes, land reclamation and urban development over the decades have resulted in significant changes to the estuary and surrounding wetlands with almost no wetland habitat remaining today and a mix of stormwater pollutants and flooding impacting the communities connection with the harbour and surrounds.

Following significant flooding, Porirua City Council and Wellington Water developed a project to initially investigate viable options to manage future flood risks and subsequently expanded this to include opportunities to retrofit water quality improvements for the CBD area.  

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Morphum Environmental were initially engaged to look at opportunities to retrofit water quality interventions into the developed CBD. We identified a shortlist of six locations where existing stormwater could be intercepted to divert and treat flows – one of those was in Elsdon Park. This presented the ideal opportunity to co-locate a constructed wetland system with a dedicated flood detention area and design the new realigned stormwater pipeline as a cost-effective bypass to protect the wetland in high flows.

Morphum worked collaboratively alongside GHD (undertaking flood works) to design the 1 ha constructed wetland system which receives stormwater inflows from the Urukahika Stream and provide robust water quality treatment prior to discharge to the harbour.

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The wetland was officially blessed and named Te Kukuwai o Toa by Ngāti Toa in June 2022.  Morphum looks forward to watching its establishment over the coming months.

Read the full project story in the July/August issue of Water here.

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