By ROSALEEN MACBRAYNE
OPOTIKI - An Auckland University engineering research team has come up with a diversion scheme to prevent flooding at Opotiki.
The small town, which is a gateway to the East Cape, is vulnerable to flooding as it is surrounded on three sides by the Waioeka and Otara rivers.
Although stopbanks, built in 1964 and since upgraded, protect the town on most occasions, there is still a big risk if both rivers peak together.
It was a near thing for Opotiki two years ago when one river had its highest flow for 40 years, but the other one was much lower.
The answer, say the engineers, is to reroute the Waioeka River.
"The diversion would provide a more efficient way for the rivers to flow out to the sea, relieving the present river geometry which exacerbates the flooding problem," said Dr Bruce Melville, the university's head of civil and resource engineering.
A proposed 300m diversion would have the rivers meeting at an angle on the western side of Opotiki's town centre.
The regional council, Environment BOP, contracted the engineers to build a large-scale model and do laboratory tests on a range of flood flows to find the best alignment.
Philip Wallace, the council's project engineer, said the university's engineers had come up with a feasible idea after two months of testing.
"It's not going to be the only solution but it could be quite a big part of it," he said. Further stopbank work would also be necessary.
Environment BOP would now work out the cost of the project and look at environmental and practical concerns.
Mr Wallace said a rough estimate for the diversion work was from $500,000 to $700,000.
It would be up to affected ratepayers whether the project went ahead, but earlier this year most had been in favour of going ahead with the university investigation.
"If everyone gives approval, we would look at starting it early next year."
Opotiki mayor Don Riesterer said it all depended on cost.
"You can throw millions of dollars at a thing like that, but this community hasn't got millions," he said.
Mr Riesterer was part of a busload of Opotiki people who went to Auckland last week to inspect the university research model.
He conceded that the river diversion project made good sense.
"But whether we can afford it is the subject that has still to be discussed."
AdvertisementAdvertise with NZME.
Latest from New Zealand
Downloads spike for app helping EV owners track road-user charges
The platform will soon launch a feature that automatically buys road-user charges.