$15K for rock revetment will 'restore confidence' in the community

Hastings District councillor Ann Redstone with WOW Inc chairman, Keith Newman, pictured where a rock revetment will be built to combat erosion. Photo / Warren Buckland

Members of a lobby group who have long been campaigning for action to be undertaken at Cape View Corner believe a rock revetment will "restore confidence" within the community, but should only be seen as the "stepping stone" to further work including a groyne field.

WOW Inc Chairman Keith Newman says the wall, which will be similar to that at Clifton, will provide "interim protection" from further erosion "currently undercutting the landward section" either side of the number 3 ("the little greenhouse").

He says with each storm event, erosion continues to place infrastructure, including power, located three metres from the edge, water mains, and fibre-optic cabling, as well as essential access to Te Awanga and Clifton at "greater risk".

"When storms hit they most often take large chunks, not small increments."

Newman said the sea wall, "if well engineered like Clifton with large limestone rocks and access to the beach (for beach scraping etc) on the southern side, would prevent further erosion for 5-10 years and provide a very attractive edge.

"This option has to be far less costly than risking damage to or failure of essential infrastructure at the corner or waiting to see what happens if we wait another three years for construction of a groyne field to begin."

But Dr Willem De Lange, of the Earth Sciences faculty of University of Waikato, who has studied the coastal erosion in the area, says building seawalls, revetments and groins are "at best a temporary solution".

"It's just how substantial a structure you build that determines how long it is before you have to do it again.

"The main issue at Haumoana is that the gravel ridge the houses are built on is gradually moving inland during storms," De Lange said.

In the 1970s, it was suggested the houses should be moved inland to the other side of the road, but De Lange says the owners refused.

He said the reason nothing has worked so far is because there is not enough sediment to effectively trap to achieve anything.

'When you're dealing with a mixed sand-gravel beach like you've got at Haumoana, its effectiveness is debatable because generally, the gravel material is travelling at the upper part of the beach in the storm berm and unless you build the groyne to the full height of the beach, you don't stop that movement."

The revetment and armouring of Cape View Corner would be funded by HDC and supported by DOC, which owns the sections either side of the "green house".

Hastings District Council group manager planning and regulatory services, John O'Shaughnessy, advised that there is a reserve available for the replenishment work and there is sufficient funds in the current reserve to fund the next 12 months, at between $15,000 to $20,000.

He said there will be a need to allocate further funds in 20/21 and onwards, to sustain the replenishment need and to allow beach crest scraping on the Cape Coastal Ridge.

The Council's annual plan will be adopted at the full council meeting on June 27.