Characterising the post-seismic behaviour of damaged slopes - Nepal 2015

The intense ground-shaking experienced during the 2015 Nepal earthquakes triggered over 3,000 landslides, and left many other mountain slopes heavily damaged. The earthquakes occurred in the winter dry season, a period that is year-on-year relatively inactive in terms of landsliding. Over 80% of rainfall in Nepal occurs in the monsoon, and as a result over 90% of fatal landslides also occur during this period. The risk of destabilizing heavily-damaged slopes that have extensive networks of cracks - that may develop into landslides during the monsoon - needs to be fully understood. The basic understanding of landslide mechanisms, and in particular the behaviour of slopes and landslides after earthquakes, is at present limited by a lack of direct observations of how slopes and landslides change in the months that follow.

In this project, working in collaboration with colleagues at the National Society for Earthquake Technology in Nepal, we aim to collect a unique dataset on the changes to cracked slopes during the forthcoming monsoon rainfall. By monitoring landslide movement and how this responds to the monsoon rains, we aim to develop a] new understanding of which types of slopes remain stable, and which continue to move and develop further landslides. Based upon our previous research on landslide mechanics, we will use this data to consider possible future styles of movement and controls upon this process, with a view to improving our understanding of landslide movement, but also to feed directly into earthquake-triggered landslide hazard and risk assessment, both immediately in Nepal, and more widely to other regions that may face similar hazards in the future.

Our proposal seeks to address a scientific gap in understanding of slope failure mechanics. A stark practical demonstration of science's relatively poor understanding of post-earthquake (EQ) landslide risk and action based upon this is the lack of a landslide equivalent of the earthquake 'Duck, Cover, Hold' protocol. We argue that this is rooted in a lack of science on how slopes are likely to behave after earthquakes, and how we should manage the risks they pose. This is despite the relative familiarity with landsliding resulting from pervasive rainfall-triggered landslides during each monsoon in S Asia. Whilst we will seek to maximize immediate impacts to Nepal at every opportunity, the greatest impacts are likely to be gained from our analysis of the slopes during the months after the EQ. Our findings will be beneficial in mitigating landslide risk in future earthquakes in countries with similar EQ and landslide hazards. We anticipate the following outputs, with the potential for impact: A tool-kit for responsive monitoring EQ-damaged landslides; Evidenced-based guidelines on the performance of EQ-damaged slopes; Capacity-building of local specialists in landslide monitoring; Long-term monitoring of post-EQ slopes beyond the end of the project; and, Scientific outputs on EQ-triggered landslide mechanics and hazards.
We will conduct the following to maximise the potential for impact:
1) Hold a workshop in Nepal to share the findings with: key stakeholders in the communities in the Upper Bhote Koshi Valley; district and village-level government officials and humanitarian/development professionals in Sindhupachok; national level government; and, the development community in Nepal. We will aim to share our data and interpretation to underpin a tailored analyses for each group. The outcome will be greater awareness of the potential insight gained from monitoring for landslide disaster risk reduction.
2) We will develop training materials explaining how to monitor slopes. The research will enable us to install equipment across a limited number of sites but there is scope for stakeholders to install similar systems in other locations. We will work with NSET who have extensive experience in public engagement across S Asia.
3) Our primary pathway for impact will be via the Nepal Risk Reduction Consortium's Communications Group. The NRRC draws together humanitarian and development partners with financial institutions in partnership with the Government of Nepal to reduce Nepal's vulnerability to natural disasters. Possible outlets for our toolkit include the NRRC's 'Be Prepared' platform: www.beprepared.nrrc.org.np/. We have engaged with NRRC during the EwF Project, and since the 2015 EQS. The outcome will be greater awareness in Nepal of possible post-EQ landslide failure trajectories and mechanisms to collect data to assess this.
4) Via collaboration with our extensive partner network in Nepal and S Asia, we will disseminate our findings to donor agencies, UN organisations, NGOs and local government to better understand landslide process, mechanisms, and possible future slope behaviour. Realistically, the data is a first step in better understanding these processes, but we anticipate that during the monsoon useful field data to inform decision making on slope failure risks will become available. The outcome will be enhanced links between the UK researchers and key organisations in Nepal.
Beyond Nepal, we will look to develop a Case Study for the UNISDR STAG (Science and Technical Advisory Group) on landslide disaster risk reduction (see: www.preventionweb.net/english/professional/networks/public/stag/#Case_Studies). This will include information on monitoring slopes following earthquakes and data interpretation. We will share examples with the popular humanitarian news network, IRIN. The outcome will be a freely available case study on the project, the methods for slope monitoring and the interpretation of the data gained.