GNS Science says councils should be more proactive to avoid costly and potentially fatal landslides.
The institute has updated its land-use planning guidance which suggests ways councils should manage the risks of future slips.
“Events over the last year have shown that the risk from landslides is substantial,” Engineering Geologist Dr Saskia de Vilder said.
This weekend marks one year since Auckland’s devastating Anniversary Weekend flooding, and is just a few weeks before the first anniversary of Cyclone Gabrielle which caused destruction throughout the entire country.
“Landslides on average cost us about $250 million a year. The cost from Cyclone Gabrielle that’s attributed to landslides is $1.5 billion.”
She said councils had to start considering landslides earlier in their decision-making processes.
“The main recommendation is that councils undertake susceptibility mapping, and what I mean by that is they identify areas they think might be susceptible to landslides,” she said.
“Not only where a landslide starts, but what they might impact downslope.”
That early work could save millions of dollars in repairs if future weather events caused slips, she explained.
“One of the main reasons that we’re releasing this guidance is to make sure that we use land use planning as a tool to reduce our risk from landslides,” she said.
“Once they’ve identified areas where landslides might occur they can start to do further analysis, or change how they zone land or what activities they allow on that land.”
de Vilder said prospective homeowners should have access to information about potential landslide risks.
“Landslide hazards [should be] considered early on, so when people are looking at purchasing land there might already be information available from the council about landslide hazards,” she said.
GNS Senior Natural Hazards Planner Scott Kelly said it was important to bring the guidance up to date.
“It’s not about preventing development,” he said.
“It’s about having the right information to inform the right development in the right place.”
He hoped smarter planning could prevent the catastrophic damage seen throughout the North Island in early 2023 from happening again.