Regional flood hazard assessment

Flooding impacts more people, more often than any other natural hazard in Wellington Region. It damages property, blocks roads and puts lives and livelihoods at risk. 

Flooding is projected to become more common and severe in the future, as climate change brings more frequent and intense storms.  

In March 2023 we completed an assessment of flood hazard across the region. 

This assessment was completed to help inform strategic and policy decisions. It isn’t intended for property-level decision making. But will be used if no other flood hazard information exists or it is the best available information.

See the regional flood hazard assessment map

If you would like detailed information about flood risk where you live, please see our separate flood hazard map. 

Focus of the regional flood hazard assessment  

Our focus is on understanding the likely impact of a: 

• Significant, but infrequent, flood 
• Which has significant climate change impacts 

You might hear the significant, but infrequent, flood we’ve assessed called a ‘1-in-100-year-flood’. But that’s not quite right because there isn’t one of this size flood every 100 years. 

It’s more accurate to call it a flood that as a 1% chance of happening in any given year. (Or, in technical flood protection language – it’s a flood with a 1% Annual Exceedance Probability or AEP).

How could this assessment be used?

This assessment has been completed to help inform: 

• Relevant policies 
• Emergency management planning.

It will be used to provide flood hazard advice if no other flood hazard information exists, or it is the best available information.

Some examples of what this assessment could be used for include: 

• Informing urban planning rules so people avoid building homes in areas that are vulnerable to flooding 
• Encouraging investment in measures to reduce flood risk is flood prone areas 
• Supporting regional initiatives to adapt to climate change.