A recent nationwide study led by Earth Sciences New Zealand has found that more than 750,000 people in New Zealand currently reside in areas vulnerable to flooding from one-in-100-year rainfall events.
Projections indicate that this figure could surpass 900,000 if the country experiences an additional 3 degrees of warming, underscoring the growing impact of climate change on flood risk.
The research estimates that $235 billion in building assets are exposed to such flood events today, with potential exposure increasing to $288 billion under the higher warming scenario.
Infrastructure is also at risk, with 26,800 kilometres of roads, 14,100 kilometres of stormwater pipelines, and 21% of national grid sites currently exposed. These numbers could rise to 30,800 kilometres, 15,400 kilometres, and 29%, respectively, with further warming.
Dr Emily Lane, programme leader and principal hazards scientist at Earth Sciences New Zealand, said flood risk is increasing throughout the country, including in places without a previous record of flooding.
“This is partly due to climate change – we know rainfall intensity is increasing across Aotearoa, with more rain falling in shorter periods. Rapid urban intensification is another contributing factor,” she said.
The study highlights significant regional variation in flood exposure. For example, 8% of Taranaki’s population is currently exposed to one-in-100-year rainfall events, compared to 34% on the West Coast.
The findings are the result of a five-year collaborative research programme involving multiple stakeholders, including research institutions, government agencies, and industry partners.
A major outcome of the project is the launch of a nationally consistent flood hazard viewer. This tool provides new floodplain maps for 256 regions, using a standardised approach to model flood risk under both current and future climate conditions.
Dr Sam Dean, principal climate scientist at Earth Sciences New Zealand, noted that more frequent and intense rainfall events linked to climate change represent a major hazard for the country.
“The building of our towns and flood defences have been shaped by historical floods that are no longer a reliable guide to the future. Predicting how flood risk is going to change is important to ensure we can protect people and places that we value in the most cost-effective way,” he said.
The new flood hazard viewer is designed to support policy development, risk assessment, and investment decisions at the national level.
It complements existing local and regional flood maps, providing broader coverage and filling information gaps.
Lane noted that while the tool does not replace detailed local models, it enhances comparability and helps identify areas where further analysis is needed.
Graeme Campbell, river management advisor for Te Uru Kahika – Regional and Unitary Councils Aotearoa, said the tool improves the consistency of flood hazard assessments and supports collaboration among regional experts.
In tandem with the research release, the New Zealand government has introduced its first National Adaptation Framework.
The framework outlines a coordinated approach to managing climate-related risks, with a focus on clear roles for government, the private sector, and communities.
Local councils will be required to develop 30-year adaptation plans for areas most at risk from flooding and coastal hazards, detailing actions, costs, and funding strategies.
Kris Faafoi, chief executive of the Insurance Council of New Zealand (ICNZ), said the framework clarifies responsibilities and emphasises the need for timely action.
Climate Change Minister Simon Watts outlined four pillars for the framework:
A National Flood Map is planned, with the first version expected by 2027, to provide accessible information on flood risk for the public and industry.
