UAV technique to localize landslide susceptibility and mitigation proposal: A case of Rinchending Goenpa landslide in Bhutan

Abstract

Natural hazards such as landslides impose very high risks to the community and infrastructures. To mitigate such risk, proper long-term engineering solutions are must. Several studies conducted in the past proposed countermeasures on many occasions. Despite such interventions, the Rinchending Goenpa area still suffers high vulnerability to landslide hazard which continues every monsoon. To assess landslide characteristics in detail, we performed landslide susceptibility mapping using the unmanned aerial vehicle (UAV) technique and conducted a site investigation. High-resolution digital elevation model (DEM) was generated with the site-specific aerial photographs and processed in Agisoft PhotoScan to developed thematic layers in geographical information system (GIS) software. We implemented a multi-influencing factor (MIF) for deriving the influence of landslide conditioning factors and developed a landslide susceptibility map (LSM) using the weighted overlay method (WOM). The landslide conditioning factors include slope, elevation, aspect, topographical wetness index (TWI), and normalized difference vegetation index (NDVI). According to LSM, the areal coverage of landslide susceptibility of study area reveals 2.41% in very low susceptibility, 37.14% in low susceptibility, with highest in moderate susceptibility zone of 49.55% followed by 10.60% in high susceptibility zone, and 0.30% in the very high susceptible zone. Based on the zonal distribution of LSM, and considering findings from several other site investigation such as geophysical survey, the performance of existing countermeasures, soil characteristics, and footprint of last landslide occurrences, we proposed mitigation measures under each zone to provide long-term solutions.