Assessment of mountain slope instability in the Lish River basin of Eastern Darjeeling Himalaya using frequency ratio model (FRM)

Abstract

Landslides are the most destructive natural hazards that undermine the economic and cultural development in Darjeeling Himalaya. To prepare landslide susceptibility map of the Lish River basin of Eastern Darjeeling Himalaya frequency ratio model (FRM) was applied based on remote sensing and GIS tools and an integration of ten landslide triggering parameters or factors like Geomorphology, lithology, slope angle, slope aspect, slope curvature, drainage density, NDVI, Relative Relief, land use and land cover (LULC) and soli map were made. The frequency ratio model (FRM) was used to derive class frequency ratio or class weight incorporating both pixels with and without landslides and to determine the relative importance of individual classes. All the data layers were prepared in consultation with SOI Topo-sheet (78B/9), Google earth image, Landsat 8 OLI (operational land imager), GDEM (Global Digital Elevation Model) image with the help of Arc View and ARC GIS Software (10.1). A Weighted linear combination model was performed to combine frequency ratio/class rating values and to determine the landslide susceptibility index (LSI) value on GIS software tools. Greater the value of ‘LSI’, higher is the propensity of landslide susceptibility over the space. Then, the Lish River basin was classified into six landslide susceptibility zones, i.e., very low, low, moderate, moderately high, high and very high considering the ranges of LSI.