New National Flood Map Reveals Over 750,000 New Zealanders at Risk

Nationwide Flood Risk Unveiled

A groundbreaking national flood map, released by Earth Sciences New Zealand (formerly NIWA) on October 29-30, 2025, has revealed that more than 750,000 New Zealanders are currently living in areas susceptible to major flooding events. This figure represents approximately 15% of the country's population and is based on a one-in-100-year rainfall or river flooding event. The comprehensive data also projects a significant increase in this risk, with the number of exposed individuals potentially rising to over 900,000 should global temperatures increase by three degrees Celsius.

The new flood hazard viewer is the culmination of a five-year research program aimed at providing a nationally consistent understanding of flood risks across Aotearoa. Dr. Emily Lane, principal hazards scientist at Earth Sciences NZ, emphasized the importance of this data, stating, 'Our country's flood risk is increasing, and not just in places where we can remember floods occurring. 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.'

Economic and Infrastructure Vulnerabilities

Beyond the human impact, the new map highlights substantial economic and infrastructural vulnerabilities. The research indicates that approximately $235 billion worth of buildings across New Zealand are presently exposed to flood risk. This valuation is projected to escalate to $288 billion under a scenario of three degrees of additional warming.

Critical infrastructure is also significantly exposed. Currently, 26,800 kilometers of the nation's roads, 14,100 kilometers of stormwater pipelines, and 21% of national grid sites, such as substations, are at risk from flooding. These figures are expected to rise to 30,800 km, 15,400 km, and 29% respectively, with a three-degree increase in global temperatures.

A Tool for Adaptation and Planning

The newly launched flood hazard viewer provides a consistent, street-level view of flood risks, filling critical data gaps and improving the comparability of flood hazard assessments nationwide. This tool is intended to support national policy development, risk assessment, and investment planning for climate adaptation. It allows individuals to assess their local risk and how it might change under future climate scenarios.

While local and regional councils have historically developed their own flood maps, often with varying methodologies, this national viewer offers a unified perspective. The New Zealand government is also developing an official National Flood Map, anticipated for public release by 2027, which will integrate rainfall, river, and coastal flood risks, building upon the foundational work of Earth Sciences New Zealand.

Regional Disparities and Future Outlook

The research also revealed significant regional variations in flood exposure. For instance, the West Coast shows the highest exposure, with 34% of its population currently at risk from one-in-100-year rainfall events. Regions like Hawke's Bay, which experienced severe impacts from Cyclone Gabrielle, are projected to see their exposed population rise from 22% to 31% with just one degree of warming.

Experts hope this consistent national data will guide better decisions on where to prioritize climate adaptation efforts and where to avoid future development, ultimately enhancing the country's resilience to the increasing frequency and intensity of extreme weather events.