Abstract
Landslides are one of the most destructive and most recurring natural calamities in the Himalayan region. Their occurrence leads to immense damage to infrastructure and loss of land, human lives, and livestock. One of the most affected regions is the Bhutan Himalayas, where the majority of the landslides are rainfall-induced. The present study aims to determine the hazard and risk associated with rainfall-induced landslides for the Phuentsholing region located in the southwestern part of the Bhutan Himalayas. The work involves developing a landslide risk map using hazard and vulnerability maps utilizing landslide records from 2004 to 2014. The landslide hazard map was generated by determining spatial and temporal probabilities for the study region. The spatial probability was computed by analyzing the landslide contributing factors like geology, slope, elevation, rainfall, and vegetation based on comprehensive field study and expertise about the area. The contributing factors were divided into various classes and the percentage of landslide occurrence under each class was calculated to understand its contributing significance. Thereafter, a weighted linear combination approach was used in a GIS environment to develop the spatial probability map which was multiplied with temporal probabilities based on regional rainfall thresholds already determined for the region. Consequently, vulnerability assessment was conducted using key elements at risk (population, land use/land cover, proximity to road, proximity to stream) and the weights were provided based on expert judgment and comprehensive field study. Finally, risk was determined and the various regions in the study area were categorized as high, medium, and low risk. Such a study is necessary for low-economic countries like Bhutan which suffers from unavailability of extensive data and research. The study is conducted for a specific region but can be extended to other areas around the investigated area. The tool can serve as an indicator for the civil authorities to analyze the risk posed by landslides due to the rapid infrastructure development in the region.
Highlights
Landslides are considered one of the most prominent and devastative natural disasters leading to immense loss of human lives and infrastructure [1]
Landslide hazard is the probability of a landslide event of a certain magnitude within spatial and temporal limits [11], whereas landslide susceptibility is the likelihood of landslide occurrence depending on local conditions [37]
The temporal probability is calculated by multiplying annual exceedance probability and the probability of landslide occurrence
Summary
Landslides are considered one of the most prominent and devastative natural disasters leading to immense loss of human lives and infrastructure [1]. Geosciences 2020, 10, 131 landslides is either rainfall or earthquake of which rainfall-triggered landslides can be categorized as very high and intense. Of global fatal landslides [2]. Landslides in the Himalayas occur mainly due to monsoonal precipitation leading to huge financial loss and often disrupting the only livelihood of people [3,4]. The global fatal landslide database developed by [2] shows a total of 64 deaths in Bhutan due to nonseismic landslide events from 2004 to 2017, but the actual number of deaths is expected to be very high. The menace is expected to escalate because of the cutting of hills and deforestation emphasizing infrastructure development linked to a rise in population
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