New Zealand’s Natural Hazards Commission says new slope stability guidelines will help identify and assess landslide risks, which have grown in recent years.

Since the Auckland Anniversary floods in February of last year, landslips have accounted for more than $NZ302 million ($352.36 million) of losses – four times more than all other natural perils combined.  

Richard Justice, lead author of the Geotechnical Society’s new guidelines, says they aim to avoid confusion, because the “lack of a good practice document can sometimes lead to the same slope being evaluated by different people with completely different results.

“For years, New Zealand’s geotechnical community has been calling for clear and consistent advice on how to conduct site investigations and hazard assessments for landslides, and we’ve made a big step in that direction through this new guidance. This guidance reflects the huge amount of knowledge and research in New Zealand and internationally, [ranging across] land use planning, investigation, model development, stability assessment and mitigation.”

He says further guidance will focus on recognising landslides, field investigations, analysing unstable slopes and mitigation strategies.  

“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.”  

Natural Hazards Commission principal adviser Wendy Saunders says the information is vital because many New Zealanders live on slopes and “we can expect to see more landslips if nothing is done to mitigate risks”.