University of Auckland associate professor of applied geology Martin Brook went to check the damage in Shore Road in Remuera following Cyclone Gabrielle. Photo: RNZ / Mohammad Alafeshat
An expert on landslides and natural hazards warns much of New Zealand may become "uninsurable" in the future.
However, quantifying risk from natural hazards is a fraught business - especially when it comes up against property rights.
The storm that triggered a massive slip in Lower Hutt last winter and forced the evacuation of three cliff-top properties was a shock to residents - but not the council.
Only the year before, it paid $35,500 (plus GST) to engineering consultancy WSP for an analysis of unstable slopes across the city, including Eastern Hutt Road.
That report - obtained under the Official Information Act - refers to previous studies dating back to 1977.
Geographic information scientist Associate Professor Mairead de Roiste from Victoria University said there was no national standard for assessing landslide risk - or for communicating it to the public.
"There were some councils in New Zealand that just didn't want to share that information publicly because they were concerned about a backlash from homeowners in those locations.
"There were other councils [that] felt we need to communicate that information generally, because obviously there's a risk implication."
The 2022 slip on Eastern Hutt Road, the main road to Stokes Valley. Photo: Supplied
LIM reports (land information memoranda) were highly technical and could be difficult for lay people to understand, she said.
Furthermore, people's interest in information could depend on their personal circumstances, such as "whether you own a house, versus whether you're trying to buy a house".
The government is trying to fix this ad hoc system. The Local government Official Information and Meetings Amendment Bill will require councils to put natural hazard information on LIMs, including the impact of climate change.
Natural hazards expert Associate Professor Martin Brook from the University of Auckland said the bill was "well-meaning", but many councils would not have the money or the expertise for the enormous task involved in putting it into practice.
"Set up a national geotechnical control office with teeth, funding and proper expertise. Get them to do this on a national level and then get them to disseminate the information to various councils."
Local Government New Zealand president Stuart Crosby agreed the government would need to chip in.
"Some of these councils are very small and cannot do it on their own. But also, there is infrastructure - roads, schools, hospitals - where they are also the beneficiaries. So it doesn't seem unreasonable that the government should come to the party."
Local Government New Zealand president Stuart Crosby. Photo: Supplied
It was not only technical support they needed, but legal, he said.
"There have been examples where a council would say 'No, you cannot build in that particular area.' It's gone to the Environment Court and got turned over and they've said, 'Yes, you can, with certain conditions.' And in some cases, that's been a recipe for disaster."
However, disasters are quickly forgotten, even within a generation. Brook said houses were still being built on dodgy slip-prone land - as the Auckland anniversary weekend floods and Cyclone Gabrielle had shown.
"It's councils wanting to get re-elected, it's governments both right and left not wanting to make hard decisions that are in the best long-term interests of the country. It's like a re-run of a bad movie.
"But if New Zealand becomes uninsurable, that's a problem for all of us."
To get the economy of scale necessary to fix the problems, he suggested a radical solution: "The clause is still there for New Zealand to become a state of Australia, it's in the Australian constitution… [It would mean] a lot more capability in terms of emergency management and scalable science and all the rest of it. And maybe that's something that has to be considered."
Hutt City Council has told RNZ new slope stability hazard maps and planning controls would be included in the draft district plan, which will be up for consultation later this year.
Head of planning Tim Johnstone said data from all past landslips "of which the council is aware", is already provided in LIM reports.