Landslide Hazard Zonation in Darjeeling Himalayas: a Case Study on Integration of IRS and SRTM Data

Landslide Hazard Zonation (LHZ) mapping of the Darjeeling Himalayas in Eastern India has been taken up by the Geological Survey of India to demarcate various zones based on their susceptibility to failure and suggest remedial measures. In this article, the various spatial data sets utilized and different digital techniques adopted in susceptibility mapping, the results of the GIS-based modeling studies following the BIS (1998) guidelines on macro-scale landslide zonation are described. The limitations of Digital Elevation of Models derived from topographic maps and IRS pan stereoscopic satellite imagery through digital photogrammetry are explained and the utility of 3-arc second Shuttle Radar Topography Mission (SRTM) DEM data to overcome those limitations in the highly rugged hilly terrains such as the Darjeeling Himalayas are discussed. Five zones in the order of increasing susceptibility are demarcated by GIS vector data overlaying techniques on the basis of Landslide Hazard Evaluation Factor (LHEF) rating scheme. The validity of this susceptibility zonation vis-a-vis existing landslide inventory is briefly dealt with and adoptability of BIS LHEF rating scheme while employing GIS-based modeling studies are critically evaluated.