Impact of geofactors on landslide susceptibility using weighted overlay method: An integrated GIS and field-based analysis on NH-07, Chamoli, Uttarakhand

• Knowledge driven weighted overlay method used for susceptibility mapping. • Field and GIS maps were ranked and rated based on the vulnerability for landslides. • Integrated approach of WOM for land-use planning and disaster risk reduction. The Himalayan Belt is notably at risk for landslide occurrences, which are directly related to the region's development and economic well-being. The study area encompasses Tangni to Vishnuprayag road sector, National Highway-07 (NH-07) in Chamoli district of Uttarakhand. The primary objective of this study is to identify the zones susceptible to landslides within the region, thereby contributing to the reduction of landslide disaster risks. Knowledge driven weighted overlay method (WOM) integrating GIS and field based multiple geofactor maps has been used where each thematic map was given a rating and weighting process utilizing a heuristic approach which facilitated the generation of a landslide susceptibility map, separately for the rock and debris domain of the region. Seventy-three landslides along the road corridor and its surrounding areas, establishing a correlation between their spatial distribution and various geotechnical parameters have been considered for this study. The resulting susceptibility map documenting 73 nos. of landslide incidences in the study area indicates that low susceptibility zone accounts for 49% of the area accomodating 8% (06 nos.) of the total landslide incidences. The moderate susceptibility zone accounts for 30% of the area but has 19% (14 nos.) of the total landslide incidences and the high susceptibility zone accounts for 21% of the area but has 73% (53 nos.) of the total landslide incidences. Validation of the susceptibility map was conducted against historical landslide data and field observations, which confirmed its reliability. This integrated approach of WOM serves as a significant resource for land-use planning and disaster risk reduction in landslide-prone areas of the Himalayas. Furthermore, it illustrates the efficacy of the WOM for mapping landslide susceptibility, providing a replicable framework for similar terrains both within the Himalayas and in other regions.