Lower Hutt is the most densely populated flood plain in New Zealand. The city has a history of flooding, and the projected effects of climate change makes flooding a complex natural hazard to manage.
Flood hazard mapping
To give us a clearer understanding of flood risks in Lower Hutt and better prepare for the future, Wellington Water (which manages water services for the Wellington Region’s councils) is modelling the likely impacts of extreme rainfall on the urban areas of Lower Hutt.
- is done to best practice standards,
- takes into account the forecasted impacts of climate change out to 2120, and
- is being peer reviewed by independent experts.
The resulting flood hazard maps depict flooding in 1 in 100 year and 1 in 10 year floods. They show:
- where waterways are most likely to breach their banks,
- where water moves across land during flooding, and
- areas of ponding.
The work represents the most comprehensive flood hazard mapping in the city’s history. It is expected to be completed in 2021. The modelling of urban Wainuiomata is the first model to be completed.
The maps will help reduce the impact of flooding by giving Council, the community and government agencies a better understanding of future flood events. This means we can improve infrastructure, our urban planning and our responses during extreme rainfall events.
An important part of finalising the maps is asking local people about their experiences of flooding on their properties and in their neighbourhoods. Wellington Water staff will be showing the maps to residents and seeking their observations and photos of past events at public drop-in sessions to ensure the maps are as accurate as possible.
What will Council do with the information?
The overarching aim of this project is to protect life and property.
The information provided by the maps will be incorporated into the review of Hutt City Council’s District Plan, which includes the land use rules for Lower Hutt. This review is about to get underway. Council has a responsibility to ensure future developments avoid flood prone areas and do not make flooding risk worse for existing properties.
All councils are required to make natural hazard information public. Any property with a history of flooding will have this information added to its Land Information Memorandum (LIM).
The flood hazard maps will provide crucial information for the forward planning of storm water and other infrastructure in Lower Hutt. They will also be an important resource for local Civil Defense planning.
What happens next?
The first modelling to be completed is of urban Wainuiomata. To ensure the maps are as accurate as possible, Wellington Water and Hutt City Council will be holding two public drop-in sessions.
These will enable residents to view the maps, ask questions about the project and provide their observations and photos of past flooding events. Wellington Water is keen to know where water flowed or settled in residents’ neighbourhoods and properties during past flooding events. This information will be used to fine tune the maps.
The drop-in sessions will be held at the Wainuiomata Intermediate School hall on:
- Thursday 5 December 6pm-8pm
- Saturday 7 December 2pm-4pm.
For more information on the flood hazard mapping project, see the frequently asked questions or contact Wellington Water at: firstname.lastname@example.org