Cheaper Radar Units A Game Changer For Coast Flood Monitoring

Wednesday, 12 March 2025, 7:41 am
Article: Lois Williams - Local Democracy Reporter

New radar technology is making it easier - and cheaper - for hydrologists and Civil Defence to keep an eye on rivers around the West Coast and predict floods.

The West Coast Regional Council now has a network of about 50 telemetry sites tracking rainfall and river levels.

Hydrology manager Samwell Warren says about 12 sites have been added in the past year.

His team now has a pretty good picture of what the rivers are doing from Karamea to Haast, and looking east, to Arthurs Pass and Maruia, he says.

“There are some gaps – in places where there’s no way to get a radio or cell signal out, or the river changes course too much. But overall, it’s working well."

Advances in technology have been game-changing for the council, Mr Warren said.

“The number of monitoring sites has gone up and down a bit in the past depending on budgets – it used to cost $30,000 to put a site in. But you can put a small radar unit on a bridge now for just $1400.”

The data coming from the radar units might not be as accurate for science purposes but they were cheap, easy to read and more than fit for purpose for flood prediction, he said.

One of the new radar units was installed recently at the Callery River in South Westland, a tributary of the notorious Waiho (Waiau) River at Franz Josef.

“It’s very flashy - the river goes up and down fast, and the catchment’s steep and prone to slips. So if it’s raining in the catchment and there’s no change in water level at the radar site, that could give us a warning if a landslide has blocked the river and formed a dam.”

The data would be relayed back to the hydrology team by telemetry via the cell network, Mr Warren said.

Three of the newer monitoring sites were funded by the government through the Resilient Westport project: one on the State Highway 67 bridge over the Buller River; one on the Orowaiti River bridge and a wave buoy offshore.

The new Inangahua River telemetry site at Blacks Point has replaced an old one further downstream that was no longer viable, Mr Warren said.

“The banks were crumbling; there were access issues and once the hydro scheme starts drawing water we’d have had to calculate how much and add it to the total for an accurate reading.“

The rebuilding of Reefton’s historic hydro scheme by a local trust is almost complete and it may start generating power in the coming weeks.

Anyone interested in river levels and rainfall in their community could view current and historical readings on the West Coast Regional Council website, Mr Warren said.

“The interface went up a few years ago and a lot of our farmers and councillors like keeping track of what the rivers are up to in their areas,” Mr Warren said.

-LDR is local body journalism co-funded by RNZ and NZ On Air.

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