Slow drainage from Te Awanga lagoon caused much of the flooding around the township last week, but councils disagree about who is responsible.
Heavy rain overnight on April 26-27 exceeded the capacity of the Leyland drain running through the area. The drain, as well as water running overland, overflowed into the lagoon.
Hastings District Council spokesman Paul Evans said the drain and all urban stormwater was the district council's responsibility but the lagoon and its outlet was the Hawke's Bay Regional Council's.
"The Leyland drain could not handle the amount of stormwater," he said. "This was statistically 50 per cent more rain than a 100-year event."
A 100-year event consisted of 260mm in 48 hours. The area got 382mm over two days in last week's storm.
The lagoon drains into the Maraetotara River, but high flow restricted the outlet. That outlet was "100 per cent under the regional council", Mr Evans said.
Hawke's Bay Regional Council asset management head Mike Adye said it was not clear who was responsible for the outlet.
Regional Council staff working in the area called a digger to clear a channel from the lagoon to the ocean about 10am Wednesday. Water receded soon after that outlet was opened.
"I think there does need to be another outlet, but whether it's in that location and how it's managed will need consultation and discussion," Mr Adye said
The river itself did not flood towards Te Awanga, it over-flowed south as was intended when the stop banks were built.
Flood risk management consultant Bill Syme, from Queensland, said while some mitigation such as levies could be done to prevent flooding, education was most important for big events.
"There is always going to be an event bigger than your levies," he said.
"That's when it comes down to people knowing what to do."
Auckland City stormwater projects manager Grant Ockleston said one benefit of local body amalgamation was an ability to share resources and improve infrastructure.
"With multiple councils you have different standards and different resources," he said. "It doesn't need to be amalgamation but there should be a mechanism for councils to work together."
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