Opinion: Lots of work in and around Mangaone Stream

Penny Gaylor.

Weekly column by Kāpiti's Greater Wellington Regional Council representative Penny Gaylor.

Earlier this year a public meeting was held in Te Horo to discuss the flooding event last December, and the concerns and impacts of flooding, in particular related to the Mangaone Stream.

At the start of this month I organised a smaller meeting to report back on the action taken by GWRC and KCDC officers since the public meeting.

Thank you to Liz Koh for hosting the report-back meeting which was attended by the chairs of the two Te Horo Friends groups and a local farmer, and they'll work through their groups and contacts to also convey this information.

Here's a roundup of the short, medium, and long term actions, either done, under way or planned.

In the short term GWRC have been clearing streams, and GWRC cut the mouth at Te Horo beach in early May. Clearing is due again early August.

As a medium term, and ongoing action, the consent application for clearing of highly modified water courses is under way. GWRC has sent letters informing landowners of the consent process. The consent application is due to be lodged by the end of June.

We thought the consent would be non-notified, but now understand it might need to be. If it is to be notified, the consultation will be more significant and it will include the affected communities.

GWRC will advise the wider community if there is any need for the community to submit on the application, but for now we are looking at a non-notified consent so submissions will not be required.

KCDC has also undertaken various short term action. They have checked the visibility at the bridge by the corner of Te Horo Beach Rd and Pukenamu Rd, and confirmed that visibility is minimum standard.

The KCDC team has cut back vegetation as much as possible to help this. KCDC believe they own a further 5m back that they hope to be able to cut back as well.

KCDC noted that every sump in Te Horo beach was cleaned in June 2021. That was part of their annual clean. Though there is one that hasn't been cleaned because it was lost in the system. A local resident showed KCDC where it was, and they're clearing it so it is more visible and to make it function better.

The Nicholas St intersection is a problem, and KCDC have put new platforms around and replaced some sumps in this area, and are upgrading the asset to make sure water isn't coming down Kitchener St.

KCDC reported back that this area is 2.5m above sea level, and the water table is 500mm below ground level so soak pits won't work in this area. KCDC estimate that It might be up to $100k for a major improvement here, and have spent $25k recently to "get stuff done".

For the medium term, KCDC has commissioned a study regarding what's going on with Jewel Creek. There's a 2.4m culvert, followed by a 1.6m, and then the Te Horo Beach Rd culvert is only 1.05m in diameter (as coming downstream).

KCDC noted that they need to understand the impacts of upgrading the 1.05m culvert to 1.6m. If the impacts are acceptable, then KCDC can get it into the forward work programme, which is likely to be in 3-4 years.

For the long term, GWRC are building a flood hazard model of the area. This is of course part of our planning for climate change. And then, once we have that modelling, we can use it to check the impact of culvert upgrades.