$10m flood protection scheme proposed for Westport

5:24 pm on 21 July 2021

A $10 million flood protection scheme proposed for Westport would have prevented most of the devastation caused by last weekend's massive flood, according to West Coast Regional Council's operations director Randal Beal.

Proposed stopbanks and floodwall system for $10m Westport protection scheme which would effectively ring fence the town

Photo: Supplied / West Coast Regional Council

The council has included the Westport project in its 2021- 2031 long term plan which is yet to be released to the public.

But Beal said the scheme involved extensive stopbanks and floodwalls - essentially ringfencing the town from the Buller and Orowaiti rivers and would cost $10.2 million.

"It is designed for a one-in-a-100-year flood in the Buller ... and whether it would have protected the town this time, the simple answer is yes, unless there was a flood bank failure," Beale said.

"There would likely still have been surface flooding damage to some properties from storm water but not to the same extent or over widespread areas."

The regional council originally pitched the project to Westport ratepayers in 2017 - but they had little appetite for it, Beal said.

Only 10.8 percent of respondents supported it; 24.6 percent preferred to do nothing about their town's flood risk and 30 percent had no opinion.

"It would have been an expense for ratepayers, certainly, and without a majority supporting it we couldn't go ahead," Beal said.

The Regional Council also tried pitching the Westport flood protection scheme to the government last year, for funding as a shovel-ready project but it was turned down.

The town was granted a small amount to upgrade its flood warning telemetry system, while larger grants went to stopbank projects in Franz Josef, Greymouth, and Hokitika.

Buller Mayor Jamie Cleine said Westport would need to renew its discussion about flood risk but last weekend's event had set new benchmarks for the kind of protection the town would need in future.

Sixty-five homes had been red-stickered or condemned by late Tuesday, with more likely to suffer the same fate after the raging Buller sent floodwaters surging into the Orowaiti, and overland across farms and low-lying residential areas.

Buller High School and surrounds in Westport, flooding, 17 July 2021

Flooding at Buller High School and surrounds in Westport on 17 July 2021. Photo: Supplied/NZ Defence Force

Cleine said the flood defied all previous modelling and some ideas that had previously been put forward as solutions to protect the town would have been of little use.

In a letter to local papers last week, former Westport Mayor Pat O'Dea berated councils for failing to remove gravel from the bed of the Buller and keep the Orowaiti overflow clear of vegetation.

"I believe the Buller River poses a major threat to the lives and property of the people of Westport and its immediate surrounds..councils are doing nothing to fix the problem, which

is the riverbed getting continually higher."

The riverbed at low tide was higher than at any time in recent decades and the Orowaiti overflow was completely overgrown, O'Dea said.

"All this will see the river cut through behind the O'Conor Home and flood many areas of Westport ..the engineers that designed the harbour and the town's protection would turn in their graves to see how the area is at risk because of the lack of maintenance of the critical safety valves."

But Cleine said no amount of gravel removal or clearing willows would have stopped what happened last weekend.

"In a flood this size the river bed becomes irrelevant - the water is metres above it and in this case, the volume and force of the water was so great, even the high tide had no effect on it.

"Usually you get a surge and peak at high tide - but not with the Buller - not this time - it just kept pushing out to sea and there was no difference in the flooding level - that's how huge it was ."

Westport people will have a chance to reconsider the $10.2m stopbank and floodwall plan for their town, and a second cheaper option with partial stopbanks, when the regional council's long-awaited long-term plan is released for community consultation.

At this point the LTP with details of a potentially hefty general rate rise, is still with the auditors.

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