Far North townships 'saved' from flooding thanks to flood protection work

Joe Carr and district councillor Felicity Foy at the Whangatane Spillway. Flood prevention work is being credited with keeping Kaitāia above water. Photo / Supplied

An upgraded flood plan has saved two Far North townships from going underwater last week, with the region's rural inhabitants hardest hit by last week's deluge.

Kāitaia and Awanui received 150mm of rain in just 48 hours last Wednesday-Friday in the most severe flood event since 2007.

According to the Northland Regional Council, its $15.5 million Awanui River Flood Management Scheme had prevented significant flooding to the urban areas of Kaitāia and Awanui.

The almost 20-year-old project was designed to help future-proof the decades-old scheme, including predicted climate change impact.

The goal of the scheme was to prevent a large flood in urban Kaitāia potentially causing millions of dollars of damage and putting lives at risk.

This meant increasing the protection of Kaitāia to a 1:100 year flood and nearby rural areas to a 1:20 year level of protection.

Before the scheme, a flood like that of July 1958 had seen 1m standing waves flowing down Kaitāia's main street, with vast areas of rural farmland under water for weeks.

According to the NRC, this latest storm had been between 15 to 30 per cent bigger, with no flooding to Kaitāia and greater protection to the rural areas.

Former regional councillor and Awanui River Flood Management Liaison Committee chair Joe Carr agreed both townships would have "disappeared" underwater if not for the upgrade.

"In terms of Civil Defence, Kaitāia was and still is the most at-risk town in the Far North for flooding," Carr said.

"It was therefore vital these flood works proceeded.

"As a result of the flood protection, all of the urban areas in Kaitāia and Awanui were saved from going under.

"I'm really pleased with how well the system has worked," he said.

At the peak of the rainfall last week, Carr spent the night monitoring the Awanui River.

He said the event had been the first real test of the flood scheme.

While the larger urban areas were saved from floodwaters, some low-lying areas of Awanui were not so lucky, with several homes on Kumi Rd going under last week.

Carr explained flood protection work in that area was due to have been finished by summer and would have made a significant difference.

"There are definitely still areas that need structural change," he said.

There is also still significant work to be done down near Donalds Rd Bridge where the flood protection needs to be lengthened.

"The main worry, for now, is for the farming community in these lower regions, particularly near Kumi Rd and the Whangatane Spillway," Carr said.

"These farmers won't be feeling very positive, but in the bigger scheme of things, it's done the job it's meant to do."

Among those affected by the floodwater were Will and Marianne Tye.

The couple have farmed on Kumi Rd for seven years, with three dairy farms totalling just over 1000 cows on 200ha.

Thursday's torrential rain flooded 95 per cent of their first farm, half their second farm, and 20 per cent of the third, forcing them to move stock to cow sheds on dry ground.

They said the increase and volume of water had taken them by surprise.

"We've never seen so much water here in all the time we've been here," Marianne said.

"Right now we're quite concerned about the impact this will have on production, particularly on the grass," Will said.

Awanui's Will and Marianne Tye with daughter Zara outside their dairy farm on Kumi Rd. Photo / Myjanne Jensen

"If the grass remains wet for more than a few days that could have disastrous consequences for our business and income.

"We feel that the flood protection scheme has done things a bit backwards.

"They've started upstream, but it's here where the water ends up and there's more now than we've ever seen before."

The Tyes believed if the flood works had started at the lower end of the catchment, the volume of water would have been less severe and more evenly spread out.

Flooding in Northland is likely to become more intense as climate change continues.

This will increase risks to communities in flood-prone areas and to critical infrastructure such as roading.

Far North District councillor Felicity Foy visited some of the worst-affected houses over the weekend.

Her mother, Fiona King, a former Far North District councillor, helped form the Awanui River Flood Management Liaison Committee.

Foy said she was grateful the scheme had done its job, even if it hadn't been able to protect everyone from the floodwater.

"My huge interest in stormwater is in my blood where 'drainage, drainage, drainage' was instilled in me from a young age," Foy said.

"Projects like this have a long legacy and we've got to be able to push this through, from scoping and funding through to delivery.

"Our communities deserve better and to be protected.

"I really feel for the families who've been significantly impacted and it's just really unfortunate the works weren't completed where they were hit.

"Hopefully we can stop this from happening again."

An NRC spokesperson said given the amount of rain last week, the council would usually expect to see the river breaching and flooding at Kaitāia supermarket Bell's Produce.

This was prevented, however, due to bank stabilisation, benching and major tree clearance work completed in the area earlier this year.

The spokesperson said it was important to understand bigger events would continue to overwhelm flood defences even after the upgrade was completed.

"Since 2006 NRC has completed major work in the Lower Whangatane Spillway and Lower Awanui River, including removing major blockages, topping up stopbanks and setting stopbanks back where possible," they said.

"After the short-cutting of river loops in the 1960s, the riverbed has been scouring due to increased velocity, causing the stopbanks to become unstable.

"If we had not addressed these structural issues there was a real potential for a stopbank failure sending water through Kaitāia, affecting hundreds of houses and businesses."

NRC's hydrology team was said to be currently compiling data collected during the event to assess the full impact of the flood protection works.

More work was scheduled to be planned for the Lower Whangatane Spillway, to top up banks and set back stopbanks.

The scheme upgrade is scheduled to be finished by June next year.

Due to the nature of the scheme occupying a flood plain, however, work to protect Kaitāia would never be fully completed.