Helen Punton wants Wellington Regional Council to make a cut in the Waikanae River mouth to protect homes from dune erosion

Dune erosion at northern Paraparaumu Beach. Photo / David Haxton

A concerned resident fears homes are at risk unless a cut is made in Kāpiti’s Waikanae River mouth.

Helen Punton said the river mouth had moved south creating fluvial erosion which lowered the beach and impacted dunes at the northern end of Paraparaumu Beach.

She had lived in the area for over 20 years but since 2017 had been in contact with Greater Wellington Regional Council because she believed the erosion was getting worse.

Her concerns had been heightened, especially over the last six months, as the erosion had “gone crazy”.

“I’m hoping there’s not a lot of high winds this winter.”

Punton had spoken to one of the house owners who she described as “devastated” by the dune erosion.

She said the issue wasn’t about climate change as there was accretion “on the same beach around the corner”.

“It’s the river mouth that’s doing it [northern end dune erosion].”

A cut would involve digging a channel through a beach or spit to realign the river channel.

She said there had been a cut every six and half years on average for 70 years but the last mechanical cut was by the regional council in 2001.

Northern Paraparaumu Beach where there is dune erosion. Photo / David Haxton

A cut could be permitted when the river exceeded trigger points which meant if it migrated 500m south, or 200m north, of a groyne on the south bank of the river, or if erosion seriously threatened private dwellings.

“They assure me they will cut the river mouth when the trigger points are exceeded.”

Punton had received correspondence from the regional council via Official Information Act requests.

Environment group manager Lian Butcher wrote there was a dune buffer 25m to 50m between the houses and the beach that was “providing sufficient protection to properties at the northern end of Paraparaumu Beach”.

The erosion was occurring as a “result of natural coastal and fluvial processes”.

The river mouth was monitored “on an annual basis and at times when a severe weather warning is issued and following flood events”.

“No action has been considered necessary from those inspections.”

Butcher said the regional council would cut the mouth “when the triggers are reached and the risk is accessed to require a mouth cut”.

Specific records of the river’s position in regards to trigger points weren’t maintained, he said.

Any decision to cut the mouth would be undertaken “with discretion in order to minimise disturbance to the habitat of the estuary and coastal environment”.

“The aim is to allow the river mouth to operate as naturally as possible.

“Specially the cuts are to be used for the purposes of flood and erosion control within the river mouth and estuary.”

The river mouth was also part of a scientifc reserve that is managed by the Department of Conservation so any cut would need approval from the Minister of Conservation.

Butcher said it was distressing to see dunes eroded but the current phase of erosion “is not yet directly threatening houses from being undermined and the number of intersecting variables makes it difficult to link any one process, such as erosion, with another, such as river mouth alignment, with any degree of certainty”.

Punton made a submission to Kāpiti Coast District Council’s long-term plan asking it to “act as advocates for their community and ensure GWRC acts or provide a hard engineering solution to protect its community, and its own liability”.