Abstract

<p><span>Landslide activity in the Himalaya region is hypothesized to have increased over the last decades, as suggested by exiting landslide databases and disaster inventories. This trend has been linked to an enhancement of heavy rainfall events under warming climate, but also to anthropogenic factors that influences the slope stability as well as to an increase of exposed of people and infrastructures in prone areas. Yet, as recognized by the Intergovernmental Panel on Climate Change (IPCC), such positive trends are still unclear, mostly due to the lack of baseline data with enough spatio-temporal resolution. Focusing on Far-Western Nepal, we draw on remote sensing techniques to create a multi-temporal regional landslide inventory for the period 1992-2018 over an area covering 6,460 km2. To this end, we systematically interpret geomorphologically high-resolution satellite imagery from Google Earth. Besides, we analyze multispectral differences from Landsat images to interannual date the initiation or reactivation of the interpreted landslides. This massive effort includes the digitalization of 26,350 landslide events, of which 8,778 were dated at an annual scale. These events serve as a basis for the analyses of landslide frequency relationships and trends in relation to annual precipitation and temperature datasets, derived from ERA-5 climate reanalysis.</span><br><span>Our results show a strong correlation between the annual number of shallow landslides and the accumulated monsoon precipitation (r=0.74). Furthermore, warm and dry monsoons followed by especially rainy monsoons produce the highest incidence of shallow landslides (r=0.77). However, we find strong spatial variability in the strength of these relationships, which is linked to recent demographic development in the region. This highlights the role of anthropogenic drivers, and in particular, road cutting and land-use change, in amplifying the seasonal monsoon influence on slope stability. In parallel, the absence of any long-term trends in landslide activity, despite a widely reported increase in landslide disasters, points strongly to increasing exposure of people and infrastructure as the main driver of landslide disasters in this region of Nepal. Thus, our assessment could not determine evidence for any climate change signal related to landslide activity over this part of the Himalayas.</span></p>

Highlights

  • Landslides are a major cause of destruction to lives and livelihoods across the globe, with notable hotspots of landslide risk located along the great mountain chains of the world, the Himalaya (Nadim et al 2006; Petley 2012; Froude and Petley 2018)

  • Rotational, compound, and flow slides as well as debris flows (Highland and Bobrowsky 2008) are the main landslide types found in the area

  • In this paper, we present new insights into landslide activity that was enabled through the creation of a high-resolution, multitemporal landslide inventory

Read more

Summary

Introduction

Landslides are a major cause of destruction to lives and livelihoods across the globe, with notable hotspots of landslide risk located along the great mountain chains of the world, the Himalaya (Nadim et al 2006; Petley 2012; Froude and Petley 2018). Elsewhere, heavy rainfall is often associated with landslide triggering (Kirschbaum et al 2015), with events predominating during the peak monsoon months of July–September. This clear link has led to increasing focus on climate change as a driver of past and future landslide activity (Gariano and Guzzetti 2016), given expectations for increased rainfall extremes over much of the globe (Orlowsky and Seneviratne 2011), including the anticipated intensification of the South Asian Monsoon (Kitoh 2017). Even if disaster trends are considered robust, the difficulty comes from needing to distinguish any change in landslide activity (event frequency or magnitude) from other drivers of risk such as population growth and expansion of infrastructure into exposed areas. While interannual variability in landsliding appeared to be linked to monsoon activity, Petley et al (2007) concluded that poorly planned road building was likely a key driver of this trend, highlighting broader issues around regional development in Nepal and the other mountain regions (Hearn and Shakya 2017; Sudmeier-Rieux et al 2019)

Methods
Results
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.