The New Zealand Geotechnical Society (NZGS) has issued new guidelines designed to create a uniform approach for assessing landslide risks, an area that has lacked consistency in New Zealand.
The guidance is part of an effort to address landslides, which rank among the nation’s most significant natural hazards in terms of financial loss and human impact.
Richard Justice, lead author of the guidance and a geotechnical risk specialist, said discrepancies in slope evaluations have been a recurring challenge.
“The lack of a good practise document can sometimes lead to the same slope being evaluated by different people with completely different results,” he said.
The guidance incorporates research and practical knowledge from both New Zealand and international experts, providing a foundation for improved hazard evaluations.
The first segment of the guidance, released last week, focuses on identifying landslide hazards and offers recommendations for managing unstable terrain.
Additional sections planned for 2025 will address areas such as field investigation techniques, slope analysis, landslide recognition, and mitigation strategies.
Justice clarified that the guidelines are not a substitute for professional expertise.
“We will always need to rely on our geotechnical engineers and engineering geologists. The guidance we have developed is meant to help them in their assessment of landslides – but it cannot replace experience and expertise,” he said.
The development of the guidelines was supported by funding from the Natural Hazards Commission Toka Tū Ake (NHC) and the Ministry of Business, Innovation and Employment.
The effort aligns with NHC’s mission to enhance resilience through better land management practices.
Landslides are the leading cause of natural hazard insurance claims in New Zealand, according to NHC. The Auckland anniversary floods in early 2023 alone resulted in $302 million in landslide-related claims – over four times the total cost of all other natural hazards combined.
Dr Wendy Saunders, NHC’s principal advisor on land-use planning, highlighted the risks associated with development on slopes, particularly as extreme weather events become more frequent.
“Many of us live on slopes, especially in cities where space is limited. This can be a problem after an earthquake or heavy rainfall, because if slopes become unstable and slip, they can cause damage to property and infrastructure,” she said.
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Saunders encouraged homeowners to take proactive measures to minimise landslide risks.
“If you live on a slope, there are things you can do to identify signs of potential slipping and prepare your property, like building retaining walls, cleaning your gutters, and seeking advice from a geotechnician,” she said.
She also recommended that prospective buyers use NHC’s Natural Hazards Portal to access information about past claims and potential risks tied to specific locations.
