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

Rosser, Nick, Kincey, Mark, Oven, Katie, Densmore, Alexander, Robinson, Tom, Pujara, Dammar Singh, Shrestha, Ram, Smutny, Jakub, Gurung, Kumar, Lama, Sundup and Dhital, Megh Raj (2021) Changing significance of landslide Hazard and risk after the 2015 Mw 7.8 Gorkha, Nepal earthquake. Progress in Disaster Science, 10. p. 100159. ISSN 2590-0617

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Official URL: https://doi.org/10.1016/j.pdisas.2021.100159

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.

Item Type: Article
Additional Information: Funding information: This research has been supported by the UKRI-DFID SHEAR program (201844-112) and NERC Urgency grant NE/N007689/1. We recognise the contributions of a wider group of analysts from Durham University who fed into various stages of the mapping campaign since 2015, post-mapping support from D Hodgson, N Cox, G Basyal, R Shrestha and M Brain, and discussions around the development of the mapping data with Prof T Bhattarai and Dr C Shrestha. We thank Dr P Horton for his support in the regional implementation of Flow-R for debris flow simulation at scale. We also thank colleagues at NSET (S Shrestha, G Jimee) and DFID (T Sumner and S Dugar). Datasets for this research are being archived with NERC’s Centre for Environmental Data Analysis (CEDA), in line with the requirements of the funder, in addition to the bipad.gov.np disaster information management system. The DEM data used in the numerical modelling - AW3D - is licensed via Durham University (UK), © NTT DATA, RESTEC/©JAXA. Maps and guidance notes for use in local-level planning in Nepal that arise from this research are available at: http://community.dur.ac.uk/nepal.2015eq.
Uncontrolled Keywords: Earthquake-triggered landslides, Post-seismic hazard and risk, Satellite mapping
Subjects: F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: John Coen
Date Deposited: 05 Mar 2021 12:09
Last Modified: 31 May 2021 14:38
URI: http://nrl.northumbria.ac.uk/id/eprint/45627

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