Two $4 million stopbank options have been put out for public consultation following predictions a 100-year flood in Greytown could cause $54 million in damage to private property.
A Greater Wellington Regional Council advisory committee has been examining options to prevent significant damage in the event of a major flood of the Waiohine and Mangatarere Rivers, narrowing it down to two - Option 4 and Option 7.
Option 4 would see a new stopbank built alongside the river from the end of Wood St to SH2 and a second stopbank built around Greytown, creating a channel for water to flow around the town.
Option 7 focuses on upgrading and filling in the gaps in existing stopbanks, and the creation of spillway at The Wire Shed.
Flood protection manager Graeme Campbell said options, narrowed down from seven to two, were assessed on practicality, cost and future impacts of issues like climate change and earthquake risk. Making Greytown a safer place was the core aim of the project, he said.
"A balance is going to have to be struck. The flood waters are there, and if you push them away from one place someone else is going to get them in the end. You have to make a decision for the whole community."
No residents would be displaced by the proposed works in either option, but a balance would have to be struck in the land and property that could be saved in a major flood.
Option 4 is estimated to cost about $4 million, saving about $1.3 million a year in average annual damage, and Option 4 would cost about $4.5 million, saving about $1.4 million a year in average annual damage.
Mr Campbell said community consultation was an important part of the process. "They are two quite different options and they do achieve some different outcomes for the river. We want to know which one people prefer. But we do ask the community to be patient. We need to make a fully informed decision. There's no really easy way."
Management options
Option 4
Option 7