Isabella Ngawati evacuates an Ōtiria Rd home with six-month-old Elijah during the 2020 flood while Gwen Ngawati opts to stay behind. Photo: RNZ / Peter de Graaf
The devastating floods that have swamped three Far North towns should be a thing of the past - or at least less frequent and less severe - with the opening of a multi-million-dollar flood prevention scheme on Saturday.
Ōtiria, Moerewa and Kawakawa have been battered by floods in 2007, 2011, 2014, 2018 and again in 2020.
While no lives were lost, many homes were damaged and residents' lives repeatedly turned upside down. Floodwaters have also threatened historic Ōtiria Marae, one of only a handful of fully carved meeting houses in the Far North.
The floods have been caused by extreme rainfall combined with manmade changes that force floodwaters straight down the main road into Ōtiria and from there into low-lying areas of Moerewa.
The biggest project being opened today is a 900-metre-long spillway which will divert water overflowing from Ōtiria Stream across the valley into Waiharakeke Stream, which has much greater capacity.
Part of the problem was a bridge across Pokapu Road that acted as a dam in heavy rain.
It was replaced last year with a new bridge more than three times longer, creating a far wider flow channel.
Contractors remove the old Pokapu Road bridge blamed for worsening flooding in Ōtiria and Moerewa. Photo: RNZ / Peter de Graaf
Also being officially opened today is a deflection barrier further downstream in Kawakawa, designed to divert floodwaters away from businesses in low-lying Old Whangae Road and along the town's main street.
Northland Regional Council rivers manager Joe Camuso said the $7 million spillway would not prevent flooding entirely, but floods that had been knee-deep should in future be ankle-deep.
More than half the funding came from the Provincial Growth Fund, now the Kānoa Regional Economic Development and Investment Unit, with the rest from targeted rates, the Far North District Council and the Northland Transportation Alliance.
Northland Regional Council rivers project manager Meg Tyler at a deflection bank designed to protect Kawakawa businesses from flooding. Photo: Supplied/NRC
Camuso said local knowledge provided the solution to the valley's flooding woes.
When council staff started investigating the cause of the ongoing floods around 2017, kaumātua Murray Armstrong showed them how water used to flow down the valley - and how that had changed since roads, the railway and bridges were built.
A home on Ōtiria Road surrounded by floodwaters in 2020. Photo: RNZ / Peter de Graaf
Armstrong's explanation was confirmed by computer modelling of how water would flow if those man-made barriers were removed.
"It's not unlike many places in New Zealand or around the world, where roads and railroads have been built. They get flooded, so they build them higher, then they start to deflect the overland flow paths - and that's exactly what we found in Ōtiria."
With the spillway completed, computer modelling showed water flow through the valley should now be "pretty close to pre-human conditions", though that had yet to be tested by heavy rain.
Aerial photo showing the spillway under construction in May 2023. Photo: Supplied / NRC
The spillway was expected to be active once or twice a year, Camuso said.
It had been designed to handle a one-in-100-year event, plus an extra 20 percent to allow for climate change.
The last major flood, in 2020, was regarded as a one-in-50-year event.
Camuso said the project would not have been possible without the cooperation of local landowners.
The three blocks of land where the bridge and spillway had been built were all Māori-owned, with two of them under multiple ownership.
One piece of land had four bridges and a railway built on it since the late 1800s.
"So it took us probably 18 months mending emotional bridges before we were able to build a physical bridge.
"I just really shout out to those landowners because we acknowledge what they've been through."
Camuso said most of the landowners lived upstream from the spillway so they would not get much benefit from it, though it would certainly help people downstream in Ōtiria and Moerewa.
Within those two towns there were still issues with drainage but the Far North District Council was working to improve that, he said.
State Highway 1 at the bottom of Moerewa’s Turntable Hill used to flood any time there was heavy rain. Photo: RNZ / Peter de Graaf
Meanwhile, the deflection bank protecting low-lying businesses in Kawakawa was originally due to be built next summer but had been brought forward at the community's request.
Taumarere Flood Working Group chairman Geoff Crawford said it aimed to give one-in-50-year flood protection from the Waiomio River, and had been funded with $350,000 from the Government's Cyclone Recovery Fund and $300,000 from the regional council.
The project is understood to have been completed well under budget.
The 200-metre-long, one-metre-high bank was designed to deflect water onto a wide floodplain beside the town.
Crawford sad the Old Whangae Road bridge had to be raised as part of the project, and weeds and willows had been removed along the river.
Ōtiria Marae surrounded by floodwaters during the 2020 deluge. Photo: RNZ / Peter de Graaf
In a separate project completed in 2021, NZTA Waka Kotahi removed a bottleneck in Ōtiria Stream where floodwaters used to regularly engulf a bridge on State Highway 1 at the bottom of Moerewa's Turntable Hill.
When State Highway 11 flooded near Kawakawa at the same time, the Far North was virtually cut off from the rest of the country.
The Turntable Hill project, which was fully funded by the roading agency, cost $850,000.
The bridge has not been closed by flooding since then.
Two opening ceremonies will be held today - one starting at the Old Whangae Road bridge in Kawakawa at 8am; the other at Te Rito Marae near Ōtiria from 11am.
