Flood protection in Hawke’s Bay cannot solely rely on stopbanks and more room should be made for swollen rivers to spread out and spill into, the last Cyclone Gabrielle flood review to be released insists.
The latest major review into the Cyclone
Cyclone Gabrielle review: Regional council needs to ‘make room for the river’
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The review put forward 47 recommendations including for the council to consider the “evolving global best practice” of “making room for the river”, to function alongside stopbank protection.
“For example, secondary systems including spillways, diversions and storage areas should be considered with the objective of directing floodwater to identified areas with the lowest consequences to the communities of Hawke’s Bay,” the report read.
That would allow “floodwaters to spill, flow and be stored in a controlled manner” in the case of extreme floods including when stopbanks overtop.
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The report did not recommend whether the council would need to purchase land to make room for those spillways.
However, the report stated that without “making room for the river” it could lead to a “completely impractical evacuation scenario” in future, where around 100,000 people would need to be evacuated around the Heretaunga Plains (wider Napier and Hastings area) in the case of another extreme flood being forecast.
A panel member for the review added that spillways “are not always underwater” and can be used for the likes of cropping, and he said spillways could be “a mix” of council-owned land and privately-owned land.
HBRC chief executive Nic Peet said they would “not necessarily” be purchasing land for spillways and diversions, but he did not rule that out.
HBRC chairwoman Hinewai Ormsby said there would be some “hard conversations” with landowners, as the council works on where the spillways and diversions could go.
“We have to look at the different solutions... it is not a straightforward answer to say we could buy out every piece of land we need for secondary [flood protection systems like spillways]. It has to be a partnership approach.”
River trigger levels needed
The report noted that Hawke’s Bay Regional Council alone was not in charge of making decisions for evacuations during Cyclone Gabrielle, which was the responsibility of Civil Defence.
However, the regional council did have the responsibility of providing timely advice and information to Civil Defence about the worsening weather, including from its many weather stations.
The report criticised the regional council for its communication with Civil Defence (CDEM) during the lead-up to the floods.
“The language used in communications to CDEM was not as clear and decisive as it could have been.
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“This may have affected the decision-making of territorial authorities and Civil Defence in terms of issuing warnings and initiating evacuations...”
The report noted terms like “may be a risk” in emails should be avoided, which featured in some communication to Civil Defence.
A recommendation to improve that communication was to have clear “trigger levels” at various rivers, which could help Civil Defence make evacuation decisions.
“It is noted that the council’s Flood Response Manual (2015) has no information on evacuation trigger levels for any of the rivers within the region.
“From reviewing the timeline and communications logs evacuation warnings appeared to be fairly ad-hoc during Cyclone Gabrielle,” the report read.
“HBRC should identify specific trigger levels for alerts and recommended evacuations for known flood risk areas.”
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The regional council told the review panel that “rather than trigger points being pre-set, the trigger for providing evacuation advice has been the expert assessment of HBRC’s flood forecasters”.
“That assessment is based on flood modelling, MetService forecasts, antecedent conditions, the observed levels of rivers, etc,” the regional council stated in the report, adding that was consistent with other regional councils.
Eskdale resident Dan Gale, who owns the Eskdale Holiday Park, self-evacuated his campground in the days before the deadly floods, and said the council should have trigger levels on rivers.
“That is absolutely necessary for them to be able to make decisions based on pure hard facts and not on someone’s opinion.”
He said if trigger levels had been in place on the Esk River it would have helped with timely evacuations.
“People are traumatised. They got stuck in their roofs with their kids... because no one gave them a warning. That is the impact.”
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Significant challenges faced in the cyclone included MetService rainfall forecasts being well below what actually eventuated, and telemetry from dozens of regional council rainfall and water level monitoring sites failing during Cyclone Gabrielle.
The regional council has started work to implement 22 of the 47 recommendations, including upgrading its telemetry system.
‘Lessons from the past have not been learned’
The report questioned why relatively new housing had been allowed to go ahead in the likes of Tāngoio and Esk Valley, despite large floods hitting those areas during the past 100 years.
Both those areas were badly flooded again in the cyclone, with Esk Valley suffering perhaps the most devastation of any community in Hawke’s Bay.
“The fact that there were relatively new housing developments in areas of known flood risk suggests that lessons from the past have not been learned and development has been allowed in high-hazard areas,” the report read.
“Flood risk has been underestimated in some areas due to a lack of accounting for large historic flood events, the Esk Valley and Tāngoio Beach being particularly relevant examples.”
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The report referenced the 1938 Esk Valley flood, the 1963 Tāngoio flood, and even flooding in Pōrangahau in 1941 and 1953, which had seemingly not been accounted for.
The report recommended the regional council should “urgently review” the regional policy statement to include “clear and directive objectives and policies” regarding land use management in flood hazard areas.
The review agreed with the regional council’s Category 3 zoning decisions for Esk Valley and Tangoio.
Regional council responds
Councillor Jerf van Beek welcomed the report and said it confirmed that “raising stopbanks is not the solution”.
Ormsby also welcomed the report and said it was an emotional moment for the council.
“As Hawke’s Bay and indeed New Zealand works out how to deal with the effects of climate change and more intense storms, learning from our recent experiences is critical.
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“The review has identified a range of important learnings and provides valuable recommendations.
”What all the reviews have told us is that the way we have worked for the past 30 years can’t be the way we work for the next 30 years.
“That journey has already begun and there is a massive amount of work ahead.”
The independent review was led by a three-person panel including environmental planner Phil Mitchell (chair), river engineer Kyle Christensen, and barrister Bernadette Arapere.
The full report can be found on the regional council website.
Gary Hamilton-Irvine is a Hawke’s Bay-based reporter who covers a range of news topics including business, councils, breaking news and cyclone recovery. He formerly worked at News Corp Australia.
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