Flooding battle to cost millions

FLASH FLOODS: The latest downpour turned streets into rivers in just an hour.
FLASH FLOODS: The latest downpour turned streets into rivers in just an hour.

Nelson Mayor Rachel Reese says the city will have to pour tens of millions of dollars into stormwater reticulation over the next decade to protect against more floods.

Her Tasman equivalent Richard Kempthorne says his council is already spending large amounts with more to come.

Both were reacting to Nelson Mail questions in the wake of the torrents that tore through the Victory area of Nelson 10 days ago.

It was the fourth significant flood to cause major damage in the region since 2010, shaking the foundations of frequency graphs that suggest such events shouldn't happen more than once in 50 or 100 years.

Both councils have been often criticised for rocketing debt - Tasman has breasted $170 million, Nelson's figure is around $70m - but the two mayors said stormwater and flood protection would mean more borrowing.

"We are going to have more of these events so we have to manage the risk," Reese said.

"At the moment we are looking at upgrading the stormwater systems across the city, and the dollars around them are very large."

She said the council had to assess risks and solutions and what level of cost the community was prepared to bear.

"Council debt needs to be the focus of every council in New Zealand. Those large infrastructure projects are going to be extensive, and the only way that we can do them is to borrow - and that's the right thing to do because they're inter-generational investments and they should last for 50 or 100 years."

Nelson's costings were yet to be done city-wide, but "over the next 10 years I expect us to be spending tens of millions on stormwater and flood control", the mayor said.

There were communities in other areas that wouldn't be able to afford the infrastructure required to manage risk and the Government should be thinking about a better funding mechanism, she said.

"There should be a reasonable expectation that those one in 100-year events can be catered for."

Kempthorne said the TDC's often-denigrated debt growth was largely to provide for core infrastructure.

"Going forward we're having a real hard look at it, because what we realise is, we just can't do everything that's going to be needed to prepare for these extreme events.

"We're having to make decisions about where infrastructure is required: are we going to do it, or are we not?"

The council could only afford to fund a certain amount of work and stay within "acceptable debt limits", he said.

"It will mean that sometimes there will be infrastructure that's required and we simply have to front up and say, ‘Look I'm sorry, we can't afford that here, what are the other options?'."

While the council was looking at higher-capacity stormwater reticulation in new subdivisions, solutions could come down to such things as requiring higher floors in low-lying zones, he said.

One problem area was Richmond's main street, Queen St, which became the secondary flow path when drains and streams overflowed, but there were flood-prone areas across the district, he said.

The council was already spending tens of millions on infrastructure, mostly debt-funded because the current ratepayers couldn't afford the cost.

"What it comes down to is, how can we be prepared, what are the risks we have to cover? If you look at that big event a year ago that affected Richmond and southern Stoke, you can't put in infrastructure to deal with everything."

The Nelson Mail