April update

Published 28/04/2021

We are on track towards decisions about reducing the risk of flooding in Plimmerton. 


In the Karehana catchment, the Working Group has been providing useful and thoughtful input on a long list of options that would address a number of issues contributing to flooding:

  • holding back water safely and releasing it downstream at a manageable rate (AKA ‘attenuation’)
  • reducing the flows and volume of water reaching Karehana Park in order to reduce peak flood levels in the park
  • improving flow capacity above Karehana Park in order to prevent water from ‘escaping’ the collection network
  • increasing flow out of Karehana Park in order to reduce peak flood levels, ie. bigger and/or new pipes
  • controlling, managing or eliminating 'overland flow' – that is water that has escaped from - or never made it into - the collection network
  • protecting the network from potential blockages, such as plant matter, silt, and gravel
  • a range of localised solutions that help out smaller groups of properties, ie. improved curb and channel in the road, bigger grates and pipes in specific areas.

The next step is for the specialist engineers to develop packages, or ‘grab bags’, of options that would work together to offer solutions across the top, middle and bottom parts of the catchment.

You see the minutes of the meetings here

Thanks to Working Group community members Karen Feint, Richard Bradley, Chris Griggs, Kelvin Berryman, Alicja Gear, Grace Alum, Mel Troy, Alan Dodson and Dave Anderson.

Managing the Karehana Park grate

One of the interim measures to better manage stormwater leaving Karehana Park is to design a system that will allow the grate covering the culvert inlet at the Airlie Rd driveway to be lifted when the stream is at full flow. [see main image]

Kenepuru Engineering have designed a winch to lift the grill. Wellington Water have provided some feedback and we are now waiting on a final price from Kenepuru Engineering before instructing them to start work on building the winch. Once we have a delivery date, we will share this with you.

We are also planning to sit down with the Plimmerton Fire Brigade and Wellington Water Operational team to talk through and document how to operate the winch and when it will appropriate to use it, and how we make sure that everyone stays safe when the grate is open.

James Street and State Highway 1

Porirua City Council and Wellington Water are meeting with St Theresa’s parish and school representatives on 2 May to discuss the next steps in addressing issues in this area.

In coming weeks, you will notice teams working in the drains beside State Highway 1 clearing blackberry and vegetation from the drains. Porirua City Council is managing this task, with the financial support of Waka Kotahi/NZTA.

Waka Kotahi/NZTA have also agreed to join the team working on the long term flooding resolution for the James St/Taupo Swamp Catchment Study due to kick off in July. We are please to have one of the major partners on board and contributing to the wider investigation programme.

Operational readiness

During recent heavy rainfall, Porirua City Council and Wellington Water staff turned out at 1am to follow up on a call received by our After Hours Contact Centre. The council staff member checked out the Karehana Park grate, noted that everything was flowing as expected. They also walked up Airlie Rd, across Firth Rd and down Cluny Road to check out reports of potential flooding. The Wellington Water on-call crew also visited the site and cleared a small amount of built-up debris from the grate.

If you are aware of a stormwater inlet becoming blocked, please ring the Porirua City Council Contact Centre on 04 237 5089, at any time of day or night.

For other non-urgent maintenance requests, email enquiries@poriruacity.govt.nz or download the “Antenno” app to log a job.

Consenting workshop

We held a drop-in clinic on 21 April for flood-affected residents with questions about building or resource consents as part of their repair process. We had about seven homeowners or families stop in and we talked through their individual situations and answered questions where we could.