New research commissioned by the NZ National Institute of Water and Atmospheric Research (NIWA) has found that “lifting timber buildings by 2m would be more cost-effective than building of new houses.”
However, it found that the model would not be financially viable for concrete construction.
NIWA commissioned WT Partnership to provide cost estimates for different types of building construction subject to climate change.
NIWA Scientist Dr Christo Rautenbach led the study, part of a new NIWA Future Coasts Aotearoa (FCA) programme.
The programme investigates how lowland communities can prepare and adapt to the impacts of accelerated seal levels.
According to Dr Rautenbah, the research provides essential information for homeowners living in coastal lowlands who wish to stay on their property as long as possible.
“We know that the impacts of flooding have been felt by many, and the risk isn’t going away,” he said.
“Communities must adapt, but certain solutions like relocation inland can be unpopular and seen as a last resort, so it’s important to assess alternative coastal adaptation options.”
“These initial findings indicate that some property owners may be able to stay put for longer, even considering future exacerbation from climate change, albeit with extensive modifications.”
However, Dr Rautenbach cautions that the study highlighted the complicated nature of such preparations.
There are limited specialised house lifting contractors in New Zealand, and although raised homes remain dry, surrounding land and services will still be affected.
“The study also did not include hidden expenses, such as temporary accommodation, storage costs, and the development of supporting community infrastructure such as roads, water and wastewater services.
$2B allocated for Auckland disaster recovery following intense flooding
Last week, the Auckland City Council voted unanimously to endorse in principle a $2b cost-sharing buyout package for hundreds of uninhabitable properties and other storm-related costs with the Government.
Under the deal, the Auckland City Council and NZ Government will buy out 700 Category 3 red-stickered homes made uninhabitable by the Auckland Anniversary weekend storms and Cyclone Gabrielle in January 2023.
According to Dr Rautenbach, rising sea levels and intense flooding caused by climate change could put thousands of NZ houses at risk.
Lowland homes could be uninsurable thanks to rising sea levels
According to a 2021 report, lowland coastal homes could be deemed uninsurable over the next few decades, with the NZ government grappling with how it will foot the bill.
“By having an increased sea level, you will inundate more of the coast – so your coastline is automatically shifted landward,” Matt Rivers, a senior coastal engineer for Auckland Council, told Newshub in 2021.
“[Sea level rises] allow in larger waves, and those will have greater energy because they won’t be dissipated by the shallow bathymetry offshore – so you’ll have greater wave energy coming in, which will cause greater erosion rates.”
That’s bad news for New Zealanders living by the coast.
In 2020, the Deep South Challenge examined the risk posed by rising sea levels in Auckland, Wellington, Christchurch, and Dunedin.
It found New Zealand had a small tidal range compared to the rest of the world, meaning a slight rise in sea level could have noticeable effects.
“Only a very modest amount of sea-level rise is sufficient to change the probability of a storm surge overtopping previous high-water marks,” the report reads.
Of the four regions, Christchurch will be worst affected by sea level rises, while Wellington will face the issue first.
Researchers found a full insurance retreat – when companies lift their premiums and eventually refuse to insure coastal properties due to the risk of erosion – is likely for at least 10,230 properties in New Zealand by 2050.
Belinda Storey, managing director at Climate Sigma and one of the report’s authors, says that figure is a “very conservative” estimate.
She believes the real number of properties affected by insurance retreat in the next 30 years will likely be significantly higher – and worries homeowners aren’t prepared for when it hits them in the pocket.
“People’s perception is that providing they pay their insurance premiums on time and don’t engage in insurance fraud, their insurance will be renewed indefinitely – or at least for the period that they own an asset,” Ms Storey said.
“But our research demonstrates that… insurance will start to become unavailable or very expensive, no matter how consistent you are as an insurance consumer.”
