A flood damaged house just outside Riwaka. Photo: SAMUEL RILLSTONE / RNZ
An expert panel has called for consistent, quality information on flood risk to enable people to decide whether to buy, rent or renovate properties.
But critical research into how storms are changing with hotter temperatures has been defunded, with one scientist saying New Zealand has retreated from the research right when it's needed the most.
Last year, an internationally sought-after team of scientists who specialised in understanding how global climate models applied to New Zealand were made redundant by Earth Sciences NZ, then called NIWA.
Then, the $10 million Whakahura programme for studying how extreme events are changing was turned down for further government funding after its initial five year run.
One of the scientists behind the project, Canterbury University Professor Dave Frame, says there's still a lot we don't know.
He says climate scientists are confident that atmospheric rivers of the type that devastated Auckland, Tai Rāwhiti and the Nelson area are getting 10-20 percent wetter because of climate change.
Hotter air carries more moisture, which gets dumped on unlucky victims by storms hitting from the north, straight from the tropics.
But when it comes to other storms, for example those hitting Southland or Wellington from the south, Frame says it's more complex, with westerlies and other factors also coming into play.
"Our community tend to be a little more cautious about those extreme rain events from the south," he says.
"But the funding for extreme event research has dried up almost entirely," he says.
"Really we've ground to a halt on a lot of climate modelling and extreme event research, right when there is a clear and present need for this.
"We're getting hammered by extreme events, they are the sharp end of climate change, and we are actually retreating from our ability to answer these kinds of questions."
The expert panel report says households urgently need better information, showing the expected frequency and severity of floods, and including local terrain and features such as stop banks.
Its chair, Matt Whineray, says this is the single most important step in preparing for what the panel says should be an end to property buyouts at market value after floods.
He says better data won't just inform potential purchasers or renters, but will also help owners lower their risk by raising floor levels and electrical wiring, changing floor coverings and the like.
"That's the most fundamental bit, before everybody leaps to how are you going to transition to a different approach of sharing costs after the event, the most fundament bit is that people understand and there's an agreement on how you update that, how people get hold of that information."
The report was criticised for recommending moving towards a system where people did not expect to to be compensated for the value of their property if it became uninhabitable - though Whineray clarified this week that they weren't saying people should get no financial assistance helping them recover or relocate.
Foxhill resident Graeme Burbidge diverts water to protect his property as heavy rain hits the Tasman district, 11 July 2025. Photo: RNZ/Samuel Rillstone
Sarah-Jayne McCurrach, head of risk reduction at the Natural Hazards Commission, says an existing platform - Natural Hazards Portal - lets people search for past claims for earthquake and flood damage on a property.
"You can go in, there is a map and it will give you a little green dot if a property has had a claim on it."
The commission is also running a pilot with the Bay of Plenty region to include information from council natural hazard maps on the platform.
But McCurrach says councils vary hugely in their resources and many need help modelling flood risk.
"We've got a national flood model in the making, we've got lots of data, and in some areas it's been proven to be accurate. We've had flood modeling done, we've seen Cyclone Gabrielle occur, and it's flooded where we thought it would flood. So in some places it is very well modelled and in others it's not."
Frame says for many places it will be difficult to model climate impacts down to the post code level - though in other areas the flood risk is pretty well-known.
A member of a previous panel reporting to the government, Victoria University's Jonathan Boston, says it's unrealistic to expect people to manage their own risks, when they are uncertain, and growing.
"We can't tell somebody today, that your house will be safe for the next 100 years, regardless of where it is," he says.
Better information - when it arrives - is expected to impact property prices, though previous studies suggest that buyers have short memories - and that values aren't strongly affected by hazard maps.
Boston says irrational market behaviour and herd mentality mean there may be an abrupt correction at some point, with potentially severe consequences for whoever holds the title at that time.
Environment officials are working on how make better data available, and working up options on how and whether to offer payments to those who can't sell as a result.
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