Floodwaters surge through the grounds of Ōtiria Marae, near Moerewa, during a flood in 2014. Photo: Peter de Graaf
Residents of a Northland valley hope they will be safe from future storms after the demolition of a bridge they blame for regular floods swamping their homes.
Contractors today dismantled Pokapu Bridge, west of Kawakawa, which locals say diverted floodwaters straight down the main road and into their homes in Moerewa and Ōtiria.
It has been replaced by a three-span, 60m bridge that is higher and more than three times wider than the old bridge.
The old Pokapu Bridge, which has been blamed for worsening flooding in Ōtiria and Moerewa, as seen from the new bridge. Photo: RNZ / Peter de Graaf
The rebuild is part of a $7 million flood-reduction scheme led by the Northland Regional Council and funded by a combination of rates and government grants, including the Provincial Growth Fund (now administered by Kānoa).
The other key part of the project is a 900m-long spillway designed to redirect floodwater from the valley floor into the Waiharakeke Stream, where it can safely flow out to sea.
Is is thought that man-made changes in the valley over many years, such as the construction of roads, a railway embankment and the old Pokapu Bridge, caused flooding to abandon its natural course and instead flow down Ōtiria Road into the centres of Ōtiria and Moerewa.
Jaco Cronje, who is managing the bridge project for infrastructure firm Ventia, said the aim was to keep water in the spillway during heavy rain so it did not bypass the river and end up in the two settlements just downstream.
"Ōtiria and Moerewa go underwater quite regularly. They're in a basin so the water goes in and there's nowhere for it go out again," Cronje said.
"So this stopbank and flood mitigation project will definitely assist the whānau down there not to go underwater any more."
The first of the old Pokapu bridge beams starts it journey to its new home in Whangārei’s Quarry Gardens. Photo: NRC / Matt Johnson
The new bridge over the Waiharakeke Stream had been built on multiple-owned whānau land.
Construction supervisor Troy Packer, of Kawakawa, said locals had been highly engaged with the project.
"They're really happy with how it's going. Flooding happens quite a lot here so when this is done it will help the community hugely," he said.
Concrete beams salvaged from the old bridge - each of which is 15m long and weighs 16 tonnes - will be used in Whangārei Quarry Gardens, where a footbridge was destroyed by Cyclone Gabrielle.
As soon as the old bridge was removed by crane, work would start on demolishing the abutments so the Waiharakeke Stream could expand to the full width of the spillway during floods.
The new bridge opened to traffic on October 7.
Northland regional councillor Geoff Crawford, who chairs the area's Taumarere flood mitigation working group, said the old bridge acted like a dam in heavy rain, sending water towards Ōtiria and Moerewa and worsening flooding in the area.
The entire project was due to be completed before Christmas.
It would not stop flooding completely but it was hoped future floods would be less severe.
Areas previously subjected to half-metre-deep flooding should see that reduced to just ankle height instead.
Crawford said many people and organisations had contributed to the project, including the Ōtiria and Moerewa communities, whānau land shareholders, and local kaitiaki who had worked closely with the construction crew.