New Zealand faces escalating landslide risk due to climate change

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The study collected high-resolution satellite imagery of the vast areas of the North Island that were hit by storm-triggered landslides and compared it with the weather radar data from MetSErvice to assess the influence of various variables using a logistic regression model.

The study also considered the pre-event rainfall or prior rainfall that has dropped before the storm event as this increases soil moisture and sustained heavy rain, raising the chances of slope failure.

While it is well known that steep slopes present the highest landslide risks in areas of pasture-covered, weak sedimentary rock, North Island’s East Coast, the analysis shows the rainfall variable that significantly increases landslip susceptibility.

The authors find that once the 12-hour rainfall intensity exceeded the intensity corresponding to the 10-year recurrence interval by 25 per cent or more, the mean landslide density increased more than three-fold compared to lower rainfall intensities.

Their modelling also showed how forests reduce the landslide risk regardless of slope, rainfall and rock type, proving that the use of targeted tree planting can reduce landslips.