LANDSLIDE HAZARD ANALYSIS OF THE AREA AROUND DEHRA-DUN AND MUSSOORIE,UTTAR-PRADESH

Landslides are a common natural hazard in mountainous terrain like the Himalaya. In the present study, an area of 445 sq km around Dehra Dun and Mussoorie in Uttar Pradesh has been considered for landslide haza rd analysis on a geomorphological basis. The analysis involves classif ication of the terrain into homogeneous units (terrain mapping subunit s) based on relevant geomorphic parameters, and consequently the geomo rphic processes including occurrence of landslides. The hazard in thes e units is evaluated on the basis of field settings. Decision rules fo r the allotment of a hazard score to a unit have also been framed. The data on geomorphological complexes, lithology, drainage density, reli ef and landslide distribution were used in a geographical information system (GIS) for the analysis. A final landslide hazard map with four classes - very high, high, low and very low has been prepared. Such a map proves extremely useful as a first generation map for planning det ailed surveys in the high hazard areas. The effect of human interferen ce on the environment, particularly depletion of the forest cover has been studied. The landuse/land cover data for a period of 60 years wer e analysed in a GIS to study the changes in the forest cover. The fore sted areas account only for 9% of the landslide occurrence. About 60% of the landslides are in non-forested areas that were forested in 1930 .