Hundreds of homes unliveable, as flood protection warning issued

New Zealanders can no longer rely on flood protection barriers in the face of more extreme weather events and heavier rains, an expert warns, as hundreds of Westport residents' homes have been deemed uninhabitable following devastating floods.

Dozens of West Coast residents are no closer to knowing where they are going to live following heavy floods that caused extensive damage to infrastructure, properties and farmland across Buller and Marlborough in the weekend.

Buller District Mayor Jamie Cleine said 71 homes had been red-stickered and are unsafe, owners cannot go into them and they may have to be demolished. And just over 300 homes have been yellow- stickered, so people can only enter on urgent business.

One of those whose house was uninhabitable was Rose Jackson. She called Civil Defence for help when the floodwaters rushed through her house, and was rescued by soldiers.

"It's quite amazing, you're sitting in the La-Z-Boy and you see your shoes floating by you on the current.

"Anything that was loose on the floor was floating around, moving in the current going through the house. That's when we decided 'yes, we've got to get out of here!'"

The filthy river water that flowed through Jackson's lounge was almost knee deep, and wrecked her carpet, lounge suite, bedding and curtains. Her house wasn't yet liveable, but Jackson said she was fully insured, though some of her neighbours weren't.

Authorities say the floodwater should be treated as if it was contaminated and personal protective equipment should be used by anyone handling items that have come into contact with it. And before entering flooded homes people should seek advice from a registered electrician or Buller Electricity about electrical safety.

Nearly all of the 2000 flood-damaged properties in the Buller district have now been assessed by the district's Emergency Management team. And they are pursuing housing options for Jackson and the hundreds of others staying with friends or family, or forced into evacuation centres and other temporary accommodation.

Mayor Jamie Cleine said most floodwaters had receded, and he was exploring whether campervans, motorhomes and portable homes could be made available.

IAG Insurance said it has already received more than 570 flood-related claims across its brands, including AMI, State and NZI.

Insurance Council chief executive Tim Grafton told Morning Report they expected a thousand more claims in the next few days as residents further assessed the damage.

There had been problems getting recovery materials to those affected, as the demand compounded on already-existant supply chain issues created by the pandemic.

Reliance on stopbanks creating a false sense of security - climate scientist

The country is being warned it can no longer rely on stopbanks to prevent flooding as climate change will make major weather events more frequent and more severe.

A climate station in the Hokitika catchment recorded more than 730 millimeters of rain over two days during the weekend's storm, equivalent to half of Auckland's normal annual rainfall. In Marlborough stop-bank breaches meant hundreds of people had to be evacuated.

Victoria University Climate Change Research Institute's Dr Judy Lawrence said many householders seemed to be unhelpfully deaf and blind to how the science of global warming could affect them.

She warned the government and councils should stop allowing houses to be built in at-risk areas where they are becoming reliant on ever-bigger flood protection works.

Stopbanks were giving communities a false sense of security, and with more extreme rainfall it was inevitable people would have to stop living behind them, she said.

"A stopbank has never been a perfect fix, there's always been a residual risk.

"And what happens is we have a flood is we react and we clean up, and we go back to where we were. There are tools that can be used to identify risk and help with planning long-term.

"But we need to have a conversation with the public - people are being affected, it's dreadful what we saw over the weekend. We don't want more of that, people's coping mechanisms are limited and we can't just expect to have people continually be flooded."

The Insurance Council's Tim Grafton said some flood-vulnerable communities would face rising premiums and difficulty getting insurance as risks of flooding increased.

"The big picture is ... we are going to have more extreme weather events, and unless we do something about reducing risk, then over the years ahead, insurance will respond to reflect that risk in price and exclusions.

"What we've got to recognise is that the way in which we recognise risk is not just to transfer to insurance, but [we've got to] figure out how we control, adapt, avoid and accept that risk.

"That requires efforts by central government... and local governments to make the right decisions, so that we figure out where to build, and how we build in better places in the future to reduce those risks, to enable the transfer of risk to be affordable and accessible."

Grafton said the planned passing of the Climate Change Adaptation Bill was essential to tackle the ongoing issue. The bill is among three pieces of legislation planned by the government to replace the Resource Management Act.

"Council's need that kind of framework to enable them to do stuff. What is likely to happen here is that we will be rebuilding in the same places, where the same risks exist, to the same requirements.

"What we've got to be doing in the future, more generally in New Zealand, is to think: 'How do we do this better? How do we rebuild that better to avoid these risks or at least reduce them?'."

Climatologist James Renwick said the issue needed more attention.

"The reality is that a lot of places in New Zealand are exposed to river floods.

"We're quite good at establishing populations in areas that are exposed to river floods - I can think of the Hutt Valley, Christchurch, some of the big rivers in Canterbury and the West Coast, and Westport is in a place that is quite vulnerable.

"So whether or not you move a town, or whether you can increase the resilience of the town where it is by appropriate stop banks and other engineering measures ... it's something that the city needs to think about, certainly."

He said global warming means that when areas get dry they are more likely to get very dry, and when it rains there will be more rain.

"It's true that storms have always happened and it is winter time, but the way the climate is changing it's putting more moisture water vapour in the air... and evaporation happens faster... everywhere in the world because it's warmer.

"So we're gradually pushing the odds of a heavy rainfall event up. We expect these extreme rainfall events to become more common everywhere."