Regional flood vulnerability assessment
Horizons Regional Council completed a regional flood vulnerability assessment in February 2026.
The assessment, our first ever high-level regional overview of relative risk from flooding, looked at the modelled risk to the region with specific modelled risk rankings for 52 different population centres across the region.
You’ll find the following further down this page:
Important disclaimers about the modelling work done for the assessment and what it should be used for.
The full regional flood vulnerability assessment with appendices (warning: document is 1056 pages long, but does contain an executive summary).
Associated reports created as part of the regional assessment.
The assessment gives Council a helpful tool to utilise when making future decisions on where investment could be made into flood resilience works in the future.
Central government co-funding
The regional flood vulnerability assessment was one of a range of projects Horizons was able to complete after receiving more than $4.2 million from central government’s Cyclone Recovery Flood Resilience Co-investment Fund, to build resilience to the impacts of climate change and recover from Cyclone Gabrielle. You can learn more about another one of those projects - upgrades to our environmental data monitoring network.
Disclaimers
The regional flood vulnerability assessment is a high-level overview of modelled flood risk for population centres across the Horizons Region. Given the assessment is at a high level, people should not use these findings to assess their individual property risk. More detailed analysis would be required to create data which could be used for that purpose.
The modelling used was not calibrated against previous actual floods, and the contribution of stormwater networks to alleviate flooding was not considered. Actual flooding could be quite different to what was modelled.
Horizons already has modelling for some areas, such as Palmerston North and Feilding, which is more detailed than what the vulnerability assessment provided. That modelling can be accessed via the District Advice page and/or our Public Maps.
District Advice
If you are concerned about your individual property risk, our District Advice team can help. Their job is to provide natural hazards information to the public and other councils in our region. The most common advice sought is around the risk of flooding to guide development.
Documents and resources
Maps and summaries of Regional Flood Vulnerability Assessment
This assessment aims to provide a high-level (big picture) broad overview of potential flood risk for the Region. These maps should not be used for property-level flood risk assessments or individual decision-making.
Scope and Limitations
• Provides a regional-scale overview of flood hazards for 52 towns and settlements, with additional modelling undertaken for Palmerston North, Whanganui, Feilding, and Levin.
• Not suitable for property-level assessments. Where available, more detailed local flood models should be used for site-specific decision-making.
• The model results were not calibrated or validated against historical flood events and do not include urban stormwater drainage networks. As a result, actual flood behaviour may differ from the mapped extents.
Modelling Scenarios
• Standard Events- Flood extents modelled for rainfall events with Average Recurrence Intervals (ARIs) of 20, 50, 100, 200, 500, and 1,000 years.
• Climate Change Scenarios- Climate change impacts were assessed for 200-year and larger events, incorporating temperature increases of +1°C, +2°C, +3°C, and +3°C combined with sea-level rise in coastal areas.
• Defences Down Scenarios- Modelled with flood protection structures (such as stop banks) removed to identify potential flood pathways and demonstrate the broad influence of flood defences.