Regional council seeks independent investigation into stopbank breach

Environment Bay of Plenty has commissioned an independent investigation to find out why the Rangitaiki River stopbank breached during the flooding in the eastern Bay of Plenty.

“We need to know exactly what happened so we can take steps to make sure it doesn’t happen again,” says chief executive Jeff Jones. “This is extremely important to both Environment Bay of Plenty and the communities living in the shadow of our stopbanks.”

Mr Jones says the stopbanks are designed to hold floodwater – not to fail. “The Rangitaiki River stopbank should not have breached like it did, even with the huge amount of pressure that was on it. It didn’t fail because water overtopped it, as can sometimes happen, it just blew out.”

A 100-metre stretch of stopbank breached just above Edgecumbe mid-morning on Sunday 18 July, flooding farmland, parts of the urban area, and the Fonterra dairy factory. The breach occurred a few hours before the Rangitaiki River logged its peak flow – five metres above normal and officially at 100-year flow levels – after three days of heavy rain. The Rangitaiki River stopbanks are built to 100-year flow standards.

After the Edgecumbe earthquake in 1987, Environment Bay of Plenty carried out intensive geo-technical investigation and remedial work on the Rangitaiki River stopbanks to make sure they were still safe. The regional council also strengthened them further following the major floods of 1998, when some areas of stopbank leaked water. “That we had a failure in spite of this work is a terrible disappointment to us,” Mr Jones says.

It is expected that results will be announced in about two weeks.

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