This post from Durham Geography BSc student Amy Wright tells the story of a unique student field trip to the Upper Bhote-Khosi River catchment in Central Nepal to investigate landslides in the region and the communities affected by them.
For many of you who were privy to the widespread September flooding in North East England this year, which according to the BBC was the most intense September storm in the UK for 30 years, it may be hard to imagine areas that were experiencing more turbulent weather. However, for myself and a cohort of 30 fellow Durham University BSc Geography students in their final year of study and various staff members, intense rainfall interrupted by blazing sunshine were frequently experienced on a two-week field trip in the Upper Bhote-Khosi, Nepal.
Due to heavy monsoon rains, combined with high rates of tectonic uplift, Nepal experiences a wide range of mountain hazards. Slope failure is particularly common due to monsoonal rainstorms between June and September and annual rainfall totalling 3500 mm a year in the Upper Bhote-Koshi Valley. This makes Nepal the perfect place to gain both theoretical and practical training of hazards in a dynamic environment and speaking on behalf of the group the field trip certainly did just that. In particular, being able to observe the remnants of mass movements first hand was truly breathtaking and a once in a lifetime experience. Not to mention the fact that one of the mini-buses containing some members of the group actually got stuck in a small debris flow!
Specifically, my group was interested in the behaviour of a large deep-seated landslide and how this may alter with changes in precipitation. The landslide is located on the Arniko Highway in the Upper Bhote Koshi catchment in Central Nepal. Initially, the sheer magnitude of the landslide was one of the predominant attractions part of the investigation, considering the length and width of the slide — approximately 300m and 200m respectively. This coupled with the importance of the Arniko Highway as the main trade route from China to the Nepalese capital, Kathmandu which generates the equivalent of £1 million per week, and the deleterious effects on local economy when it is inaccessible sparked our interest in this specific landslide.
We attempted to determine the nature and setting of the landslide at an individual and valley scale through geomorphological mapping and terrestrial laser scanning and by analysing differences in type and rate of movement across the landslide through tree deformation analysis. At first, purely quantitative data collection was the focus of investigation. However, after visiting the National Society for Earthquake Technology (NSET), an NGO attempting to develop and implement organised community-based approaches to managing and minimising earthquake risk across Nepal, we considered the necessity of actually conversing with members of the local community to gain insight into the day-to-day activity of the landslide.
Interestingly, these interviews provided us with some very important data regarding the landslide and highlighted the fact that the lay people actually had a good understanding of both the causes and frequency of the landslide failure. This was vital in order to gain a general understanding of the dynamics of this specific landslide in a qualitative sense.
“The water comes and within 24 hours there is a landslide, every monsoon the water comes, the land mass comes down and the water flows” (Kali Shepalin)
Three main conclusions about the nature of the landslide emerged from conversations with the local community. These were as follows:
- The landslide is unknown to fail catastrophically.
- Previously, the centre of the landslide was the most active, but had stabilised in recent years yet was more unpredictable and the northern part of the road most commonly blocked.
- Management techniques such as gabion boxes were used in an attempt to stabilise the landslide after it had failed within 10 months but are unlikely to contain the land mass.
Furthermore, although not directly related to our study of changing landslide behaviour in relation to precipitation variations, the chronic risk that the local community faces due to the location of the settlement became apparent through our discussions with residents affected by the landslide. This was exemplified by the fact that local resident Kahika Bahadurshrestha’s father and brother had been tragically killed in 1990 by a boulder 2m in diameter demolishing part of their house, which was already partially destroyed twice this year.
Despite the inherent risk posed by the landslide, the opportunity of living by the road being greater than the risk posed permeated the conversations; Kahika was able to earn a yearly salary that was above the national average through transferring goods from a vehicle on one side of the landslide to the other when the road had been blocked by slope movements.
Information gleaned from conversations with the local community provided specific information about the risk associated with this landslide, but also highlights the wider context of landslide risk. Moreover, our study suggests how local communities appreciate to some extent the causes, rates and frequency of site-specific landslides, which have a direct impact on their lives.
Finally, calls for indigenous knowledge to be integrated into disaster risk management and reduction are widespread. Initial conclusions of this study may even go as far as to suggest that integration of indigenous knowledge about site-specific large-scale landslides that directly affect local livelihoods in the absence of longitudinal monitoring data sets could be worthwhile. However, at the very least this highlights the importance of considering indigenous knowledge alongside quantitative data generated from terrestrial laser scanning and laboratory tests in order to provide a deeper understanding of this specific landslide.
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