More than 24,000 Northlanders live in locations exposed to a one-in-100-year flood event, according to new research from Earth Sciences New Zealand.
This would increase to 29,000 if there was 3C of additional warming, according to a multi-partner research programme run over five years.
Dr Emily Lane, programme leader and Earth Sciences NZ principal hazards scientist, said the research emphasised what many already knew: flooding was one of the major hazards in Aotearoa.
“We’re very exposed to flood hazard and it’s getting worse with climate change,” she said.
Lane’s comments came as Northland cleaned up from last week’s storm, which caused evacuations and road closures when more than a month’s worth of rain fell in 24 hours.
Whangārei and Far North districts were under a local state of emergency until at least next Thursday, with a second storm forecast to hit yesterday and today.
Lane said Northland was one of the areas potentially exposed to more ex-tropical cyclones and localised convective-scale events, which were expected to increase with climate change.
On top of those living in areas at risk of flooding, the research showed more people would be affected by vital infrastructure being taken out, she said.
About 17% of roads and 45% of stormwater pipes in Northland were at risk of flooding without any additional warming.
“We’re seeing this already in Northland, if the road floods and you can’t get out or electricity is down because of the storm, but the power company can’t even get in to fix it because of the flooding, more people are affected.”
Repeated flood events also had an impact, adding to the frustration of local residents and wearing down the council working on recovery, Lane said.
The Government was already acting on the research findings, committing to national flood mapping.
Lane said this was essential to help stop people building in the wrong places.
“We’re still building in places that we shouldn’t be. At a very basic level, we need to make sure we’re stopping doing that, making those right decisions.”
Flooding also needed to be considered alongside other risks, such as landslides in Northland and earthquakes in other parts of the country, she said.
While the idea of moving out of dangerous flood zones was contentious, both due to the high cost and people’s sense of place, Lane said it needed to be considered in some high-risk areas.
“It’s about having those conversations. Maybe we can’t do it now but at least think about the plan when we’re re-building.”
A resident in a flood-prone part of Ōakura agreed better planning before houses were built could have saved a lot of grief.
Ian Webster’s house on Oakura Rd was flooded on January 18 and 21, with the floodwaters damaging the ground floor of his house, his garage, cars and a caravan.
He felt glad the storm last week did not cause any further flood damage, as it was already a long wait for the insurance-paid builders to do repairs.
But Webster admitted his house, and about a dozen neighbours’ homes, should not have been built on a floodplain.
“I honestly think the houses should never have been built here.”
Webster said if he could afford to move elsewhere, he would, but he thought it unlikely he could even get back what he paid in 2014.
He hoped Whangārei District Council would help, by creating a long-promised wetland at the back of his property to help control the water flow.
The council also needed to maintain its drains, so the water flowed away properly, he claimed.
“I’m sure we can work it out to solve the problem,” he said.
The research programme, called Mā te haumaru o te wai (By keeping the water safe), brought together 23 organisations to research flooding over five years.
While the programme’s funding was finished, there was still a lot of work to do, particularly understanding the impact of climate change, Lane said.
The national flood maps would need to be constantly updated and there was a need for national-level flood forecasting, to give people better warning of the dangers, she said.
The research found with the current climate, a one-in-100-year flood in Northland would expose:
If there was 3C of additional global warming – a worst-case scenario for climate change – a one-in-100-year flood in Northland would expose:
Denise Piper is a news reporter for the Northern Advocate, focusing on health and business. She has more than 20 years in journalism and is passionate about covering stories that make a difference.