New strategy for Havelock North’s five dams and streams

A major step towards unlocking $10 million of Government funding for flood mitigation in Havelock North was taken this week, with Hastings District Council committing funding for developing a new strategy for the area’s five dams and streams.

The strategy will include the steps needed to be taken to reduce future risk in the areas flooded during the cyclone and categorised 2C, which should allow that area to be recategorised to 1 by Hawke’s Bay Regional Council. It is the same process that has been used for areas categorised 2 across the region – investigating engineering and technical solutions to reduce risk to life in extreme weather events. Hawke’s Bay Regional Council is managing flood mitigation solutions for other affected areas across Hastings, while Hastings District Council is responsible for Havelock North.

The strategy will inform business cases for specific projects related to the Mangarau Dam and stream, needed to access the Government funding.

“I am acutely aware that it has been a very long 10 months for our residents who suffered flooded homes. Everything we are doing in this space with Hawke’s Bay Regional Council is focused on finding solutions as soon as possible,” said Hastings mayor Sandra Hazlehurst.

“Our three waters and recovery teams have been keeping those most affected in Havelock North updated, however I know that our broader community is also very interested in what needs to happen across the dams and streams.”

Reports commissioned by Hastings District Council on the performance of the dams have been completed, while a report commissioned by Hawke’s Bay Regional Council on the Mangarau Stream is in draft and is expected to be completed by the end of the month.

The dam report notes that despite the amount of rain – 80 per cent more than the previous record (283mm/162mm) – the dams performed as designed; “throttling” the amount of water being released to reduce the impact on the village.

Modelling estimates that without the dam, water flow in the Mangarau Stream at the height of the storm would have been another 22 cubic metres (or 22,000 litres) a second – a 60 per cent increase in the actual flow (measured at 35 cubic metres a second).

“I’m grateful that councillors and staff in the 1970s saw the risk and had the vision and went ahead with what would have been a huge project at the time, to build the dams above Havelock North. This is the largest event since then, and without those dams I hate to think what the outcome would have been,” said Mrs Hazlehurst.

“They could not have envisaged a storm the size we have been through this year, and now that we have had an event of this significance, with serious outcomes, we need to prioritise work that will further reduce risk.

“There is considerable interest in how the five dams and the streams they feed into performed during Cyclone Gabrielle – particularly in the Mangarau Dam and stream by those whose homes were flooded, but also by the wider Havelock North community,” said Hastings mayor Sandra Hazlehurst.

Current and historic reports, technical information, cyclone rainfall and community updates are available on Council’s website: www.hastingsdc.govt.nz/services/water/stormwater/hndamsstreams

20 November 2023

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