Slips on scenic drive in near Waiatarua have trapped residents since Tuesday. Video / NZ Herald
Foundations are exposed beneath a clifftop Auckland house, as well as the piles for a palisade wall that was designed to protect the land from collapsing.
Alarming new photographs show the situation in Beach Haven has become much worse since the January 27 floods.
Ross Roberts, Auckland Council engineering resiliencehead, indicated the fate of the new multimillion-dollar house at Brigantine Dr was undecided.
The Beach Haven house after the January 27 fatal floods. Photo / Supplied
“This will be a very challenging site that will need complex and thorough geotechnical investigation to decide the most appropriate outcome,” he said.
Demolition and abandoning the site are possibilities although he didn’t specify that. Further attempts could be made to stabilise the crumbling cliffs.
Roberts said it would take some time before decisions were made. “While photographs can give an early indication, it wouldn’t be appropriate to speculate in advance of these more detailed investigations taking place,” he said late last week.
Homeowner Ben Wilson has declined to comment on the situation with his home, which has been red-stickered. He said last week he was too busy to speak about it and last year said he was consumed with family matters.
A 2020 council technical report edited by Roberts studied exposure to coastal instability and erosion. The city has more than 3200km of coastline, three major harbours, sandy beaches and hundreds of clifftop homes, that report said.
“Due to its exposed location, Auckland is highly vulnerable to the potential impacts of both coastal erosion and inundation. While Auckland’s exposure to coastal inundation is reasonably well understood and is documented elsewhere, the risk posed by coastal erosion (and consequential instability) is less well established.”
Auckland has the largest population density to coastline ratio in New Zealand so a high exposure to coastal hazards including coastal instability and erosion. These hazards can present a safety risk, adversely affect property and infrastructure and damage or destroy cultural and environmental sites.
The site near Charcoal Bay had never been built on until a 343sq m, two-level $1.12 million dwelling and palisade wall were completed at the $2.25m property in 2021, records also showed.
The Herald reported last year on the huge slip beneath the home when the land collapsed from the cliff down into the Waitemata Harbour. But in the January 27 floods in Auckland, the situation worsened and more land beneath the house slid down the cliff.
The massive cliff fall beneath 52 Brigantine Drive. Photo / Supplied
The new home was only completed in Easter 2021, the owners told the Herald on August 4 last year when the first report was published about the collapse.
Asked last year about the weight of the new multi-level house on the site the council said had never previously been built on, Roberts said then it was “very unlikely” that weight was a contributing cause.
“This house is surrounded by a piled wall and those piles were buried 8m down,” he stressed last year.
“So that house is not having any effect on the cliff. The only way the house could be affected is if it was literally on top of the landslide - and it’s not. The house shouldn’t make any difference to the cliff stability because it’s far enough back,” Roberts said in August.
“There’s been comments raised about how much concrete went into the piles and palisade wall. But the concrete went into the foundations and actually replaced rock so there’s not much difference in weight,” he stressed last winter.
It appeared the cliff collapsed last winter due to multiple triggers: “Weak rock, you’ve got the sea eroding the toe so gravity is working against you, then there’s an ongoing process of weathering which weakens the site over time and the chemistry of the rock also changes.
“Of course, we had a really wet July so the issue of moisture to the soil and rock increases physical pressure in the gaps between the breaks and as that increases, that adds a compounding effect. Changes in vegetation can have an effect but quite how much is almost impossible to quantify,” Roberts said in August last year.
