NIWA scientists say we need to put the brakes on development in coastal areas, as sea levels rise.
A new report shows almost 800,000 New Zealanders are at risk of flooding - and that number will only grow.
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Lynn Yager had to close her Kaiaua dairy for a week last year after a massive storm surge flooded it.
"It was devastating," she says.
Today she still thinks about what would have happened if the water had got any higher.
"We'd just be washed away - it'd be twice as bad as last time and take twice as long to recover from it."
She's especially worried after a NIWA report released today predicts it will only take a 30cm sea-level rise for the risk there to become extreme.
And that means coastal areas prone to floods, like in Kaiaua, will see much bigger storm surges - the kind that would completely devastate the town.
But it's not only coastal settlements at risk.
NIWA says 772,000 Kiwis are in danger of being flooded by the sea or a river, along with $147 billion worth of buildings, and 20 airports.
And those numbers are growing.
"With only a metre of sea-level rise, population and building exposure to current extreme sea levels almost doubles across the entire country," says NIWA researcher Ryan Paulik.
In terms of population, the cities of Whakatane, Napier, Lower Hutt, Christchurch and Dunedin will be hardest hit because more than 10,000 people would be affected in each.
For many in the water's path, moving is unthinkable.
"I love my shop, I love the customers. I don't want to go anywhere," says Yager.
The scientists say we should not be building new coastal developments, and local councils need to act fast to save those already there.