Terrain Analysis and Spatial Assessment of Landslide Hazards in Parts of Sikkim Himalaya

Landslides and slope instability problems are quite common in Sikkim Himalaya. Recent developmental activities in this region have aggravated the incidence of landslides to a great extent. The ongoing developmental activities, therefore, call for delineation of safe and unsafe zones.

The present study involves the preparation of landslide hazard zonation map of East Sikkim Himalaya in a semiquantitative way by evaluating various terrain factors like lithology, structure, slope, landuse and drainage in relation to existing landslides. A numerical weightage called Landslide Susceptibility Value (LSV) has been assigned to each factor and Landslide Susceptibility Index (LSI) of each category of factor maps has been catculated. Based on the proposed methodology landslide hazard zonation map of the area is prepared showing five zones of slope instability. This map may serve as a base map for any developmental activities to be planned in the terrain. An attempt has also been made to establish the relationships of various geoenvironmental factors with the landslide activity with an objective to develop an appropriate methodology for landslide hazard zonation.