A new nationwide study has revealed that flood risk across Canterbury is set to rise sharply as the climate warms, with more frequent and intense rainfall events predicted to affect thousands of residents and key infrastructure.

The five-year research project, led by Earth Sciences New Zealand (formerly NIWA), found that more than 750,000 New Zealanders currently live in areas exposed to one-in-100-year rainfall flooding, a figure expected to climb to 900,000 with three degrees of additional global warming.

Canterbury was identified to have large areas of exposed land and infrastructure, including roads, stormwater systems, and power assets.

The study’s new flood hazard viewer shows several Canterbury towns and rural plains are increasingly vulnerable under current and future climate conditions.

Click here for the new GIS viewer for flood hazard across Aotearoa New Zealand

Dr Emily Lane, Earth Sciences NZ programme leader and principal hazards scientist, said the data underscores how rainfall intensity is changing.

“Our country’s flood risk is increasing, and not just in places where we remember floods occurring,” she said. “Rainfall is becoming more intense, and rapid urban growth is adding pressure to flood-prone areas.”

The report estimates $235 billion worth of buildings nationwide are currently exposed to flooding, rising to $288 billion under a three-degree warming scenario.\

Infrastructure at risk includes 26,800 km of roads and 21% of national grid sites, increasing markedly with additional warming.

The findings come as Canterbury continues to strengthen flood defences following the devastating 2021 floods, which caused widespread damage in the Ashburton, Selwyn, and Timaru districts.

Earth Sciences NZ principal climate scientist Dr Sam Dean said the new national flood hazard viewer — which includes Canterbury catchments — is a major step toward consistent flood mapping across the country.

“The way we’ve built our towns and flood defences has been shaped by historical floods that are no longer a reliable guide,” he said.

“This new tool helps identify which communities are most at risk, now and as the climate changes.”

The viewer allows users to zoom from national to street level, providing a snapshot of areas most likely to be affected by extreme rainfall.

While it complements detailed maps developed by regional councils such as Environment Canterbury, it fills gaps in regions that previously lacked up-to-date flood data.

The project — titled Mā te haumaru o ngā puna wai o Rākaihautū ka ora mō ake tonu — was funded by the Ministry of Business, Innovation and Employment’s Endeavour Fund, and represents the first step toward a national flood map that will one day provide property-level risk information.