$2.5M Awanui 21/22 flood works under way
22 Dec 2021, 11:34 AM
The start of a fourth construction season is underway for the Awanui flood scheme with about $2.5 million expected to be spent over the next several months.
Colin ‘Toss’ Kitchen, who represents the Northland Regional Council’s most-northerly Te Hiku constituency, says the council is part-way through a staged $15M several-year upgrade expected to be complete in two more years.
A $1.22M contract had been awarded recently for work to increase the flood capacity of the Whangatane Spillway, a project the council had named ‘Northern Benching’. This work is located between State Highway 10 and Quarry Road.
Benching involves shifting or reconfiguring stopbanks to create a wide, flat area on the inside of them which can carry extra floodwaters.
Cr Colin (Toss) Kitchen, Te Hiku Constituency representative.
Councillor Kitchen says the contract will maximise the capacity at bridges on SH10, Quarry Rd and Donald Lane.
Meanwhile, about $ 1.2M of work is also planned from Matthew's Park to Switzer Bench, the latter downstream of the SH1 bridge and a bottleneck.
“The goal is to better split the flood flows between the Whangatane Spillway – which will carry two-thirds of the water in a big flood – and the Awanui River, which will carry the remaining third.
In normal, lower flow conditions all the water goes to sea via the river.
However, in heavy rain the higher flows enter the spillway – built in the early 1900s – which cuts by 12 kilometres (and roughly halves) the length of the journey the floodwaters must take to reach the sea.
Finally work will be carried out at Bedgood Park and Dunn Street including work to stabilise an existing stopbank, benching, construction of approximately 650 metres of timber floodwall as well as topping up stopbanks.
Councillor Kitchen says much of the Awanui scheme was built about a century ago, and until recent years the NRC’s attention had been on much-needed maintenance and more immediate repairs.
The upgrade programme is designed to help future-proof the scheme – including predicted climate change impacts – as well as deliver a considerably higher level of protection for Kaitaia and surrounding areas.
The regional council says without the added protection the Awanui scheme upgrade will offer, a large flood in urban Kaitaia could cause tens of millions of dollars in damage and potentially put lives at risk.
The upgrade is designed to protect urban Kaitaia in a ‘once in a century’ type flood and a 1:20 year event in surrounding rural areas.
Improvements to the scheme in recent years had already proved their worth coping with a storm in July 2020 with very little flooding despite the volume of floodwaters being the same as an event which had flooded urban Kaitaia in the late 1950s.
Councillor Kitchen says a $12.5M grant from the government as part of its Covid-19 recovery response package – the bulk of it for the Awanui scheme – had slashed the time needed to complete the upgrade and reduced the cost to the community. It was now due for completion in just two more years instead of in 2027 as originally planned.