Flood-protection project continues

A multimillion-dollar stopbank upgrading project along the Waipaoa River to protect the region from flooding continues.

People crossing bridges along the Waipaoa River at this time of the year may look below and wonder why the council is spending tens of millions to protect the city from the trickle below.

But those in the community who remember the devastation of the Cyclone Bola flooding in 1988 know how dangerous rising waters can be.

“The existing stopbank is being raised and widened to provide for climate change effects and to improve flood resilience,” senior project engineer Joss Ruifrok said of the upgrade to the Waipaoa River Flood Control Scheme being done by Earthwork Solutions.

The improvements are designed to cater for a 100-year rain event, accounting for climate change out to 2090 based on predictions of an average temperature increase of 2.1 degrees and sea level rise of 0.67 metres.

The upgrade to the stopbank on the eastern side of the Waipaoa River involves significant excavation, with project workers expecting to use over 1.5 million cubic metres of soil on the banks.

To collect and move that amount of soil, huge tractors pull trailors the size of a Tokyo apartment with a blade on the bottom, or “scoops” as they are known in the business.

The machines pick up dirt from between the stopbank and the river. Operators then drive to the top of the stopbank, deposit and compact the dirt then loop back to get more dirt, and continue the process over and over again.

Sixty-four kilometres of stopbank is being upgraded over 11 years, protecting 10,000 hectares of fertile floodplain.

The original stopbanks were built from1953 to 1967 following a severe flood in 1948.

Once the upgrade is completed the banks will be one metre higher on average and significantly wider.

Approximately 8km of stopbank has been upgraded since construction started in February 2019.

The council aims to complete another 10km by the end of summer.

The project is due for completion in 2031.

In August last year the council was awarded $7.5 million of funding from the Provincial Development Unit to accelerate the project delivery.

The estimated cost of the total upgrade is between $32 million and $35 million.