It could be described as a perfect storm - rising sea levels and cities that are slowly sinking.
Flooding in South Dunedin. Photo: RNZ
New data has revealed sea level rise will be be knocking on our doors in almost half the time expected.
The NZ SeaRise programme comprising dozens of local and international scientists launched a new website showing how New Zealand's coastline will be affected by rising sea levels and land subsidence.
Many parts of the country are slowly sinking and will see more devastating impacts within the next two decades, rather than by 2060 as previously thought, said Victoria University of Wellington physical geography Professor James Renwick.
"The reality is the coastline is moving inland, and we have to move with it," Dr Renwick said.
Faster sinking areas in Auckland, Wellington, Coromandel, Banks Peninsula, Hawke's Bay and Marlborough-Nelson are under threat.
"It's not as though we've got to sort this out by next weekend, we've still got 20 years or more to get this organised," he said.
"But the reality is that for a lot of households and communities, where they're living now, they're not going to be able to live in a couple decades."
Just 30 centimetres of sea level rise will cause once-in-a-century flood damage every year, according to the scientists.
But Renwick warns it could be higher because the NZ SeaRise measurements assume the world will meet its global emission reduction targets.
Flooding along Auckland's Tamaki Drive. Photo: Stu Mackay / NIWA
"We could definitely be in even more trouble and that's a real worry, so if you haven't seen big effects where you live yet - don't be complacent," he said.
Moving homes out of harm's way will be costly, stressful and difficult - but necessary.
Belinda Storey, managing director of research organisation Climate Stigma, said we can't avoid the facts.
"The problem is growing every day, and the longer we delay in taking action the more expensive it's going to be," Storey said.
"But taking action today is often unpopular, and it's difficult."
She said many new housing developments were being built near the coast.
"Part of the reason the market is ignoring the risk is because they're not seeing any intervention by government. People know that in a disaster that the government steps in." Storey said.
Storey said local governments have limited resources, and central government will need to provide the finances.
"In a lot of cases the councils are very small, so they don't have specialist expertise, they also have a small rate-payer base to build on."
Some councils have started to look closely at flood retreat options - notably Porirua City Council is due to release its draft plan next month to raise, remove, or relocate flood-prone homes.
The government is also seeking feedback on a six-year plan to account for the effects of climate change including flooding, wildfire, droughts, and sea level rise.
NZ SeaRise is a new five-year research programme funded by the Ministry for Business, Innovation and Employment Endeavour Fund.