Niwa team gathers flood data

4:41 pm on 22 July 2021

Niwa says data gathered before and after last weekend's disastrous flood in Westport will influence the design of any stopbanks that may be built in future.

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

Buller High School and surrounds in Westport, flooding, 17 July 2021 Photo: Supplied/NZ Defence Force

A team of scientists from the National Institute of Weather and Atmospheric Research has been working in the flood zone since last Friday, monitoring flood gauges on the Buller River, measuring the height of silt marks and gathering information on the event that saw half the town evacuated.

Hydrodynamics scientist Richard Measures says the Niwa data will also help to predict the severity and path of future floods.

"A lot of this information like silt levels on trees disappears pretty fast so we needed to get in there and gather it quickly before the next rain washes it away. The flood had followed a fairly similar path to the less severe 2012 one and the historic November 1926 one that swamped the town," Measures said.

"But that (early) one was worse because as well as pushing the Orowaiti up into that end of town the Buller River actually burst out and flowed directly into Westport - it came close to it this time but didn't quite get there."

Niwa was getting valuable data from the flood warning system set up recently with funding from the Government as one of the Regional Council's shovel-ready projects, Measures said.

"This allows us to integrate our river-monitoring with weather forecasts and rainfall data and get projections as early as possible to the Emergency Management Centre... it can

only become more valuable with time, as we build up data and experience. "

Buller Mayor Jamie Cleine says Westport people have always had their own way of predicting how big a flood they were in for and when it was likely to hit.

"We know if you measure the Buller at Te Kahu upstream you've got an hour before that hits Westport, but the scientific data will be valuable when we look at next steps."

The West Coast Regional Council will be putting forward stopbank options for Westport in its Long Term Plan shortly to be released, with the most comprehensive scheme based on earlier 2017 proposals.

Operations manager Randal Beal says the $10.2 million scheme was designed for a one in 100-year flood and would have prevented most of the serious damage to property suffered in last week's event.

But Cleine was less certain.

"I'm not convinced that the 2017 plan contemplated what we've just seen; it might not have coped in some places.

"But the Niwa data will help us evaluate that and other things like where we should perhaps be restricting building," Cleine said.

no metadata

Local Democracy Reporting is a public interest news service supported by RNZ, the News Publishers' Association and NZ On Air.

Get the RNZ app

for ad-free news and current affairs