Flood risk may leave town with $2.5m bill

Greytown residents at risk from a major flood may have to pick up half of a $5 million tab to safeguard the town.
Greater Wellington Regional Council (GWRC) said rates from across the region would cover $2.5 million, while local ratepayers would cover the other half of the cost on top of their rates over a twenty-year period.
GWRC flood protection manager Graeme Campbell said which local ratepayers would foot half the bill was yet to be decided, with the possibility all ratepayers in South Wairarapa may be charged, or just "the people that would get wet in that sort of event."
If half the bill was divided evenly between the 1500 properties directly affected, property owners faced a bill of $1666 each over 20 years.
Mr Campbell said Greytown's people and buildings were at significant risk in a large flood, and while work was being completed needed to have emergency plans in place.
The council has released a newly developed flood hazard map showing that large areas of Greytown and its surrounds could be inundated with water from the Waiohine River - up to 10 metres deep in some rural areas.
Mr Campbell said the map shows a hundred year flood. "The biggest event you would expect in a hundred years, the sort of event you might see once in your lifetime."
But current flood defences in the lower Waiohine River are only designed to protect Greytown for a 1 in 20 year flood, he said.
"The flood risk is something to be alarmed about," Mr Campbell said; up to 1 metre of water could flow through the town causing substantial risk to people and property.
The spread of the river was estimated from historical analysis, aerial mapping and rainfall and river modelling techniques, but the strength of the flow was still being calculated, he said.
"We don't know whether the flood threat is a manageable or acceptable risk yet. Some of it might be managed by building bigger stronger stop banks, or by making sure development and land use is compatible with the flood risk."
However the potential danger was clear enough for the council to fast track public awareness of the threat and preliminary work towards building bigger stop banks.
"While we are looking to put structural measures in place everyone needs to know where it will flood and have an emergency plan in place," Mr Campbell said.
The council had also fast tracked up to two years of public consultation on how the town would manage the threat.
"It's the community's property at risk so we need the community to be involved in managing the risks. We'll be talking to the people of Greytown and the surrounding areas about this to build a picture of their expectations as we go," Mr Campbell said. "The town may choose to build 50 year or 500 year stop banks, and would then need to put in place different land use measures," he said.
"We have set up a committee of locals who know the river well, along with district councillors and hapu to help with advice and gathering people's views," he said.
Work on the first structural measures is due for completion by mid 2014, Mr Campbell said.
A "forty year flood" in Greytown took place in the early 1980's, while historic information showed water going right through Greytown in it's early history as a town, Mr Campbell said.