Spend Now To Reduce Flood Risk

Scoop

22-05-2025

Spending money now will save Kaikōura from facing the full effects of a damaging future flood, says Kaikōura District Council boss Will Doughty.
The 7.8 magnitude earthquake in November 2016 dislodged a significant amount of gravel, which left the town vulnerable in a major flood, he said.
Environment Canterbury (ECan) has been reviewing its gravel management strategy on rivers throughout the region, with submissions closing last month.
While it was difficult to estimate how much money needed to be spent now, Mr Doughty said an event similar to a Kowhai River flood in 1993, which devastated the town, would have a significant long-term economic impact.
Implementing a gravel management strategy to extract excess material would help maintain the natural flow of the river and reduce the likelihood of blockages or sediment build up.
''The wandering nature of the Kowhai River and the dynamic nature of the system is a key challenge when attempting to determine the response of the river to flood events,'' he said.
''The likely damage to the town would depend on the severity and duration of the flood event, but vulnerable infrastructure such as roads, bridges, and public services could be impacted, leading to both immediate repair costs and long term economic impacts.''
ECan rivers manager David Aires said tens of thousands of cubic metres of gravel were removed from the Kowhai River to assist with reconstruction work following the earthquake.
Local contractors and Environment Canterbury's river engineers have removed a further 25,000 cubic metres in the last eight years.
ECan manages 18km of stopbanks along the Kowhai River, which are designed for a one-in-20-year flood event.
This is equivalent to around 250 to 270 cumecs of water flowing at a rate of one cubic metre per second.
Mr Aires said the Kaikōura flood protection scheme is being reviewed.
''Over the next six months we will be measuring riverbed levels so we can determine where further gravel extraction might be required in the Kowhai River as we work through the scheme review.''
Reducing flood risk in rivers has been a major focus for ECan and other regional and unitary councils, which led to the report ''Before the Deluge''.
The report was presented to the Government in late 2022, warning of the risks and costs of a major storm or flood event.
The Auckland floods and Cyclone Gabrielle, which struck in January 2023, are estimated to have resulted in between NZ$9 billion to $14.5 billion in damage.
ECan set aside $25m a year over the next 10 years in last year's 2024/34 Long Term Plan and called on the Government to contribute $38m.
Last year the Government announced $9.5m funding towards three projects, including upgrades to critical and aged flood management infrastructure across the region to make it more resilient to the changing climate.
ECan also spent $22.6m in repair work following the May 2021 heavy rainfall event, which caused widespread flooding and prompted a region-wide state of emergency.
LDR is local body journalism co-funded by RNZ and NZ On Air.