An independent report into the catastrophic failure of Edgecumbe's stopbank has found residents were not sufficiently aware of the flood risk and there was no evacuation plan.
On 6 April the Bay of Plenty town was flooded after the Rangitāiki River burst its banks.
A "wall of water" surged through the settlement forcing the evacuation of almost the entire town's 1600 residents.
About 182mm of rain fell in two days - the third highest volume for a two-day period since records began.
More than 300 homes were damaged and about 70 percent of homes were flooded.
The review, led by Sir Michael Cullen, was commissioned by Bay of Plenty Regional Council.
It was initially due to be completed by July but the review panel was given extra time due to the amount and complexity of the information.
A farmer drives through flood waters on Otaiki Road the morning after the town of Edgecumbe was flooded by a burst stopbank. Photo: RNZ/ Brad White
Delivering the findings in Whakatāne this afternoon, Sir Michael said the College Road floodbank failed because water found its way through the material underneath the wall.
He said the seepage may have been increased by flaws in the foundation fill of the wall and damage from the town's 1987 earthquake and 2004 flood.
Sir Michael told Checkpoint with John Campbell the review also found that many Edgecumbe residents were insufficiently aware of the risks of serious flooding and there were no plans for precautionary evacuation.
"It needs to be trigger points, which are much more realistic for evacuating people from those urban areas, and there's many hours available because you're getting reasonably decent information, which tells you that there are likely to be serious problems."
"Longer term we are looking to really a change of philosophy" - Sir Michael Cullen
However, he said it was not up to the panel to point blame and said no one change to the way the flood spillways or adjoining dam were managed could have prevented it.
Climate change meant that previously rare flood events such as Edgecumbe's would occur increasingly often, Sir Michael said.
The report made 29 recommendations.
Sir Michael Cullen Photo: VNP / Phil Smith
The Bay of Plenty Regional Council has said there were lessons to be learnt from the Edgecumbe flood, including having a better idea of risk and a more conservative evacuation plan.
Council chairman Doug Leeder said they were taking the findings on board.
"Going forward we have to approach the management of risk and the potential for evacuation in a lot more conservative manner.
"The event in 2004 and the event in 2017 have clearly highlighted to Regional Council and to the community that the underlying geology on which these flood banks have been built is inadequate to serve the purpose for what they are now."
"There were some trigger levels, and those levels, with the benefit of hindsight, were set way too high." - Bay of Plenty Regional Council's chairman Doug Leeder
Regional Councils with a smaller population of ratepayers to draw from would struggle to be able to afford to do the required work to prevent another flood, Mr Leeder said.
"In terms of continuing to build in the historic manner in which we have built stopbanks, the answer to that is no.
"The methodology that was used in the '60s ... has in recent years been questioned and has proved to be inadequate in terms of the geology and the cost.
"But we've got what we've got. In order to transition to something more appropriate, it's going to take a while, it's going to cost a lot of money ... but it's a journey we've got to go on," he said.
The government has made $700,000 available for flood-affected businesses in Edgecumbe and the wider Bay of Plenty.