Increases in landslide hazard across the high mountains of Asia

The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

In terms of human losses, the mountains of Asia remain the global hotspot for landslides. Whilst earthquake-induced landslides cause occasional, very high levels of loss (e.g. the 2005 Kashmir Earthquake and the 2008 Wenchuan Earthquake), the primary driver is rainfall, especially that associated with large-scale meteorological phenomena, such as the SW Monsoon. Thus, the response of slopes to future changes to rainfall patterns is a crucial element of the pattern of landslide risk model in the future.

There is a very cool and important study of the future patterns of landslide hazard in the high mountains of Asia (Stanley et al. 2024) in the AGU journal Earth’s Future. The article is Open Access, so take a look. The study has been undertaken by scientists at NASA .

In the study, Stanley et al. (2024) have used an inventory of landslides across the region to develop a Landslide hazard Indicator (LHI) model. They have then used two scenarios of future carbon emissions and resultant change in climate to model the LHI through to 2100.

The outcome are graphs that show change in LHI through time for the various high mountain ranges of Asia. This is the graph for Scenario 5-8.5, which models sustained very high levels of emissions:-

There is a huge amount of richness in this graph. Key points for me:

1. In most (but not all) mountain chains, LHI increases dramatically under this scenario. The Himalaya is of most interest given the already high incidence of landslides and elevated human vulnerability in this area – the increase is over 40% for that region;
2. The impact of climate change on LHI accelerates with time in most mountain chains;
3. In two areas (the Balochistan Ranges and the Hindu Kush), LHI rises initially, before falling, ultimately leading to a net decrease in LHI. This affects a large area.
4. The worst affected areas are the Karakoram and the Transhimalaya (which is the mountain chain to the north of the main Himalayan peaks).

Of course, in the other climate scenario, the impact is less severe but is still significant. These two maps shows the change in LHI under the two scenarios for 2091-2100 relative to 1990-2014:-

Of course, there are huge uncertainties in this type of work. Emissions scenarios on their own are complex, and these then need to be translated through to climate, precipitation and, ultimately, LHI. Landslides are sensitive to peak rainfall intensity, which is difficult to model, as well as rainfall total. Other factors will play a role, including (for example) permafrost degradation, wildfire occurrence and of course the foolish actions of humans. Large earthquakes leave a legacy of high landslide susceptibility that can last decades – and of course we should expect such events in this timescale, so in quite large areas the hazard will be modified further.

However, the implications are clear. We are facing increased landslide hazard across the mountain chains of much of Asia. Reductions in greenhouse gas emissions will make a tangible difference to the occurrence of landslides across this region. And, finally, we need to redouble our efforts to adapt to the increased level of hazard.

Reference

Stanley, T. A., Soobitsky, R. B., Amatya, P. M., & Kirschbaum, D. B. 2024. Landslide Hazard Is Projected to Increase Across High Mountain Asia – Stanley – 2024 – Earth’s Future – Wiley Online Library. Earth’s Future, 12, e2023EF004325. https://doi.org/10.1029/2023EF004325

Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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