River flooding costs upwards of $100m a year and rising - report

The Matai River breached banks in several places to flood Nile St properties in Nelson. Photo / Tim Cuff

From RNZ

The average annual cost to repair homes damaged by river floods is more than $100 million and forecast to rise, according to new analysis.

A joint report by property research firm CoreLogic and reinsurance provider Munich Re indicates the annual repair bill could rise more than 20 per cent by 2050, and in excess of 30 per cent by the turn of the century.

Munich Re Australia managing director Scott Hawkins said in a statement that New Zealand could expect to see an increase in both the frequency and severity of weather events due to climate change.

"Weather-related disasters might in sum become as destructive to New Zealand as earthquakes," Hawkins said.

"As the risk increases strongly for many regions, it is essential for communities, commercials and individuals to understand and manage their exposure to climate risks."

The analysis found 11 per cent of the 1.6 million residential properties in New Zealand were exposed to river flooding and that could rise to 17 per cent in the next 30 years.

A resident of Nile St at their property that backs onto the Maitai River, the morning after the flood swept through Nelson. Photo / Tim Cuff

Of the current properties exposed to river flooding, five per cent were within 100-year flood risk zones but were expected to rise to nine per cent by 2050.

CoreLogic head of research Nick Goodall told RNZ some parts of the country could be too expensive, with unaffordable insurance, if insurers were even still willing to offer cover.

He said that was already happening in places, with some property owners paying risk-based premiums.

"This [analysis] just shows that it's going to keep increasing as we see more of these events and more properties that are exposed."

Goodall said people should assess the risks they face, given the location of their property, and should consider moving to a place where they might be less exposed to those risks, or prepare to pay higher premiums.

He said investing in mitigation, such as flood walls, was a short-term measure, and could encourage people to live in risky areas.

Otago was identified as having one of the highest flood risks in the country.

"Otago accounts for five per cent of total national residential property value, but 15 per cent of the national annual average river flood loss," the report said.

Hawke's Bay, Manawatū-Whanganui and Marlborough would also see some of the highest increases in rebuild costs by 2050, as river floods became more frequent.

Auckland and Wellington were exposed as well, the report said.