Waiwhetū Stream

Waiwhetū Stream flood hazard mapping has been updated 

Rivers and streams are important features in the Hutt Valley. They provide a valuable connection to the environment, but they also create a risk of flooding. 

Flooding is likely to become more common as climate change brings more severe weather. So, understanding flood risk is more important than ever.  

What does the map show?    

The updated Waiwhetū flood hazard modelling can be accessed here: Wellington Region Flood Hazard Areas.

The focus of the flood hazard map is understanding the likely spread and depth of flood waters in a significant, but infrequent, flood from the Waiwhetū Stream. The mapping also incorporates the predicted stormwater flooding. 

People often refer to a flood of this size as a '1-in-100-year flood,' but we call it a 1% annual exceedance probability (AEP) flood. This means there's a 1% chance that a flood of this size could happen in any given year. It's important to understand that it doesn't mean this type of flood occurs exactly once every 100 years.

The map shows the flood extent that is expected to occur during a 1% AEP event, including with the predicted effects of climate change and sea level rise. As well as floodwater from the stream, the map also shows stormwater flooding. Wellington Water manage the stormwater network across the Hutt Valley. The flood mapping identifies areas where the flood hazard is primarily from stormwater. In these areas, more information can be provided by Wellington Water by emailing info@wellingtonwater.co.nz. They can also advise on appropriate minimum floor levels and freeboard requirements for any new buildings.    

The focus of flood hazard maps

The flood maps were created using data, community insights, expert advice and the latest technology.   

The maps will help improve public safety and reduce the risk of costly flood damage to property by:   

• Encouraging people who live in areas where flooding could happen to get flood ready.   
• Preventing people from building in areas where flooding could happen.   
• Informing how flood risk will be managed.  

As well as being available on our website, these maps have been provided to Hutt City Council to inform the development of the Hutt City District Plan as hazard layers.  

Waiwhetū Flood Hazard

For more information about the current flood mapping in the area or to request site specific flood advice, visit our flood hazard advice page.