Predicting future landslides in the Himalayas

Joshua Jones is currently working towards a PhD in landslide susceptibility in the Nepal Himalaya. Here, he talks about the potential impact of his work on communities in the country, and on him personally

"There are few other countries that are so limited by their geological setting, a problem that is highlighted by the continual, almost unavoidable, damage that landslides do to infrastructure and livelihoods across the country"

The geology and topography of Nepal are almost incomparable to anything I’ve seen elsewhere. The mountains and valleys in central-northern Nepal are almost indescribably steep and landslide-prone, with a highly complex geological structure developed through the continuing continental collision of India and Eurasia. But of more importance is the way in which Nepalese society is forced to live in such close-proximity to this extreme landscape.

A first experience of earthquakes

In September 2015, whilst still an Undergraduate, I travelled to Nepal to undertake some community development work. This was a few months after the Mw 7.8 Gorkha earthquake had devastated much of the country, and I was shocked by the continued and pervasive damage and hardship that this event caused. This experience gave me first-hand insight into the humanitarian costs of geohazards, and is my main motivation for wanting to work in geohazard assessments in this highly at-risk region.

The overall aim of my PhD is to investigate how we can better predict future landslide occurrence across the Himalayas. This involves trying to answer questions including, but certainly not limited to: How might monsoon-triggered landslide distributions change through time in response to earthquakes and human activity? How do periglacial processes, which are predicted to become more pervasive in the Greater Himalayas due to climate-change, influence landslide occurrence? How do variations in structural geology, lithology and topography influence landslide occurrence? How do different statistical methods and modelling-scales impact landslide prediction results?

I’ve spent just under 12 weeks in Nepal. Most of this was in two study sites: Langtang Valley and the Bhote Kosi River Catchment.

In Langtang, a periglacial region severely damaged by landslides triggered by the 2015 earthquake, I focused on landslide and lithological mapping. This involved spending two weeks trekking, reaching elevations of 5,000m, mapping as we trekked. These data were then used in combination with remote sensing data to quantify the controls of landslide locations in periglacial landscapes.

In the Bhote Kosi River Catchment, in which the Arniko Highway linking Nepal and China is located, I focused on structural geology and strength mapping. Again, this involved a lot of trekking and driving across some pretty extreme terrain, trying to access and assess more remote geological outcrops and landslides. These data will hopefully allow us to better understand how structural discontinuities such as faults and joints control the locations of rockfall initiation.

<p>An&nbsp;example of a perilous ‘road’ we routinely had to negotiate



</p>
<p>Rockfall damage to a house in along the Arniko Highway in Kodari, at the Nepal-China border<br></p>
<p>The devastating Langtang Avalanche, which completely buried Langtang Village, killing over 200 people<br></p>

Seeing the effects of earthquakes

My time in Nepal has undoubtedly given me a better appreciation of my work’s relevance, but also a better idea of other issues that are hindering landslide hazard management in Nepal. For example, whilst the research I and others do on these topics is clearly important, it is useless if it is not communicated to the right people in the right way. This was highlighted to me through a visit to the Nepal Government Department of Geology and Mines. This is the department that supposedly holds the country's landslide susceptibility and risk maps, but, despite various versions of these existing in the academic literature, they had almost none.

I have also been very much motivated by seeing the damage and hurt that landslides are continuing to cause across the country. For example, our wonderful guide, Ngima, who helped with my Langtang work, told me how he’d lost many family and friends in 2015 earthquake-triggered landslides. Hearing his account and seeing the ruins of entire villages buried beneath landslides really puts my research into perspective, as does seeing the highly dangerous conditions of trekking paths and roads across the country, which have little-to-no landslide protection. All of this helps me remember that the ‘science stuff’ I do is pointless unless it is translated into meaningful, useful information and/or policy.

Meeting people such as Ngima has been incredibly humbling. Being reminded that real people are massively affected by landslides provides me with massive motivation to push on with the research, and makes me super-keen to ensure that what I produce gets communicated to the right places, so the right people benefit. Going to Nepal has also allowed me to meet with people from the Nepal Geological Society, Government Departments and local Universities, so I am hopeful that this will allow the work I do to end up where it needs to be.

Continuing research in Plymouth

I’m now entering the scary realms of my third year! So, the focus now is to continue analysing all the data I have collected over the past two years to try and answer those important questions that will allow us to start developing new susceptibility maps. I plan to start by publishing my work on how earthquakes can cause time-dependent changes in monsoon-triggered landslide distributions, before incorporating this with my field data to develop final improved susceptibility models.

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