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Ideas sought for Waiohine River flood hazard

Wednesday 15 June 2011, 10:05PM

By Greater Wellington Regional Council

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WELLINGTON

Greater Wellington is asking people living on Waiohine and Mangatarere River floodplains for their ideas on how best to protect the community from the hazards of flooding.

Greater Wellington will be holding two drop in sessions for people to share their ideas at the Greytown Library on Wednesday, June 22 and Saturday, July 2, both from 10am to 5pm.

Greater Wellington Manager Flood Protection Graeme Campbell says it’s vital that the community understands the flood hazard and is involved in managing it.

“It’s the community’s property at risk and they will be the ones who will be the most effected by flooding. We’ve got plenty of information about the flood hazard to share with people. And there are people out there who know the river well and we want to hear their ideas on how to manage it.”

Mr Campbell says there will also be opportunities to develop recreational and cultural areas along the riverbanks on land managed by Greater Wellington.

Research has shown that a 1 in 100 year flood would cause more than $54 million damage to private property. Damage to roads, bridges, railways and other community infrastructure may be tens of millions of dollars extra.

Mr Campbell says many of the older stopbanks around the Waiohine River will be overtopped in anything larger than a 1 in 20 year flood event and even a small amount of overtopping will let a large amount of water on to the floodplain.

“The Waiohine River Catchment can currently get rainfall of up to 60 to 70mm per hour, which can cause intense and damaging flood events.”

A report from the National Institute of Water and Atmospheric Research predicts more intense storms will hit the Tararua Ranges more frequently, as a result of climate change.

“Based on that we can expect worse flood events, more often.”

Mr Campbell says the value of property on the floodplain has increased several times over the past few decades and climate scientists are predicting more intense and frequent flooding in the future.

“When you add those two together, it makes sense that we look at ways of better managing the flood hazard around the Waiohine and Mangatarere Rivers. There are obviously some areas that are at high risk from flooding and these should be avoided for new developments.”