Changing significance of landslide Hazard and risk after the 2015 Mw 7.8 Gorkha, Nepal earthquake

Nick J. Rosser*, Mark E. Kincey, Katie Oven, Alexander Densmore, Tom R. Robinson, Dammar Singh Pujara, Ram Shrestha, Jakub Smutny, Kumar Gurung, Sundup Lama, Megh Raj Dhital

*Corresponding author for this work

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Abstract

The 2015 Mw 7.8 Gorkha, Nepal Earthquake triggered in excess of 20,000 landslides across 14 districts of Central and Western Nepal. Whilst the instantaneous impact of these landslides was significant, the ongoing effect of the earthquake on changing the potential for rainfall-triggered landsliding in the months and years that followed has remained poorly understood and challenging to predict. To provide insight into how landsliding has evolved since the earthquake, and how it has impacted those living in the affected area, a detailed time-series landslide mapping campaign was undertaken to monitor the evolution of coseismic landslides and the initiation of new post-seismic landslides. This was supplemented by numerical modelling to simulate the future potential reactivation and runout of landslides as debris flows under monsoon rainfall, identifying locations potentially at risk. This analysis shows that landslide hazard was higher in November 2019 as compared to immediately after the 2015 earthquake, with a considerable portion of the landscape being impacted by landsliding. We show that, while pre-existing landslides continued to pose the majority of hazard in the aftermath of the earthquake, a significant number of landslides also occurred in new locations. We discuss the value of this type of analysis in informing the reconstruction and management of settlements at risk by summarizing how this work was integrated into the project Durable Solutions II, that supported communities at risk from landslides. Finally, we consider how such data could be used in future to inform risk sensitive land-use planning and disaster recovery, and to mitigate the impacts of future landsliding in Nepal and beyond.
Original languageEnglish
Article number100159
Number of pages13
JournalProgress in Disaster Science
Volume10
Early online date2 Mar 2021
DOIs
Publication statusPublished - 1 Apr 2021

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