Flooding event highlights need for resource consent to be granted

Published on 20 August 2019

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The district’s stormwater infrastructure was tested on Saturday, with heavy rain causing flooding throughout Levin and Ōhau.

An upgrade to north-east Levin's stormwater infrastructure was carried out in 2017 which included two new pumps being installed for Kennedy Drive and Okarito Avenue.

New and significantly larger 1350mm pipes were also installed in Fairfield Road and a new outfall from the stormwater main was also laid, however, this outlet currently has a penstock installed to restrict flow through it until a resource consent is granted for the discharge of this stormwater.

Horowhenua District Council’s Acting Group Manager Infrastructure Services Kevin Peel says the new infrastructure was built to the recommended Annual Exceedance Probability for residential areas, which was for a one in ten year flooding event.

“The risk and frequency of flooding has significantly reduced in the area as a result of the upgrade. However, you can expect that at times of heavy rain, like we experienced on Saturday, there will be some flooding,” he said.

The upgrade was built to handle less than 103.9mm of rain in a 24 hour period, in line with NIWA’s recommendations for a 10 year event.

While Saturday’s rainfall was less than that, for a two hour period it was significantly more concentrated.

“During a two hour period on Saturday, just under 39mm of rain was recorded at the Levin catchment. This is more than the infrastructure was built to cope with."

Mr Peel said while the new infrastructure has provided some relief for residents, the full extent of the improvements will not be obvious until the resource consent is granted and the penstock can be removed.

“Council first started the resource consent process in 2015 and we’re hopeful it will be granted in the near future."