The 2015 Gorkha earthquake caused devastation across vast areas of Nepal, killing almost 9,000 people and leaving 3.5million homeless.
However, it also triggered thousands of landslides that caused additional destruction to communities and infrastructure – and prompted landslides in the subsequent monsoon season to occur at steeper and higher hillslopes than in average years.
That is according to new research, which provided an unprecedented assessment of how landslide distributions can be affected by extreme events.
Led by scientists from the University of Plymouth and University of East Anglia, the study was developed using a database of almost 13,000 recorded monsoon-triggered landslides spanning a period of almost 30 years.
This time period included several years known to have been impacted by extreme events (storms, the 2015 earthquake and floods) and offered a unique opportunity to assess how landslide occurrence changes through space and time in response to both extreme weather and earthquakes.
The results showed that landslide distributions varied significantly over the 30-year period, particularly in the years impacted by storms (1993 and 2002), earthquakes (2015) and floods (2017).
This, the researchers say, is a problem as current risk models typically assume that landslide distributions do not change through time, and so cannot accurately forecast landslide occurrence during and following extreme events.
With landslides currently accounting for 17% of all fatalities due to natural hazards – and World Bank research suggesting more than 66 million people live in high risk landslide regions – this study highlights the compelling need to improve current landslide risk models in order to better manage and mitigate landslide hazard.
The study is published in the Journal of Geophysical Research: Earth Surface, and also involved researchers from the University of Exeter and international engineering consultancy firm, AECOM.