Geohazard characterization in Upper Bhagirathi basin: GIS computation for Landslide Susceptibility using Frequency Ratio Modeling

Slope movements are the geological hazard or a recurring phenomenon that disrupts the natural environment and causes significant property damage and human suffering almost every year. As the young Himalayas, prone to landslides due to active tectonics, face a growing threat and cannot be overlooked. Unsustainable practices like deforestation, population rise, and slope development exacerbate instability. These activities weaken slopes through reduced vegetation cover, increased erosion, and altered drainage patterns. This interplay of geological vulnerability and human pressure demands a thorough understanding of landslide susceptibility in the Himalayas and especially in study region. In the study region Upper Bhagirathi basin (UBB), it has greater influence with combination of factors derived including surficial, underground, topographic and hydrologic conditions. Geography belongs to the Northern Himalaya, and prone to such disasters. Based on the present aim of study, identification of the landslide, and vulnerable spots (Susceptibility map (LSM)) over the region was mapped using Frequency Ratio (FR) method in Remote Sensing and Geographic Information System (RS & GIS) environment. Various conditioning parameters along with the settlement density map were used to fact check and to get FR model. It gives accurate zonation over the study area. Finally, the LSM has been divided into 5 different classes, namely as ‘Very Low (19.5674
^%
)’, ‘Low (24.6021%)’, ‘moderately (24.5265
^%
)’, High (16.8657) and ‘Very High’ (14.4382
^%
) susceptible zones. Model validated using the Area under the Curve (AUC) yielded a value of 96%, indicating a highly accurate landslide susceptibility map generated by the FR model.