Landslide zoning in a part of the Garhwal Himalayas

The Himalayas are undergoing constant rupturing in the thrust belt zone in the Garhwal Himalayas, due to which earthquake and mass movement activity i s triggered. These processes of mass movement and landslides have been cons tantly modifying the landscape. Landslides are one of the indicators of the geomorphological modification taking place in this active and fragile terr ain. This work is aimed at providing another example of landslide susceptib ility mapping based on geological and geomorphological attributes. The data collected from aerial photographs, topographic sheets and the image sugges ts that there is a correlation between the distribution of landslides and s ome of the geological and geomorphological factors, for example, the distan ce from an active fault, relative relief and slope. Parameters like factor of safety, altitude, relief, slope and the distance from the fault lineamen t have been included in the study. A rating system has been applied to the factor for arriving at a quantitative estimate of landslide susceptibility for each physiographic unit. Since terrain classification forms the foundat ion of this work, the entire study can be grouped into two sequential activ ities: (1) the terrain classification and (2) landslide susceptibility mapp ing. The result is the landslide susceptibility zoning map presented. The l andslides have not been classified with respect to time and may represent t he final result of the on-going geological, geomorphological and seismic ac tivity since the Holocene period or late Pleistocene time when the glaciers retreated. The area chosen for the study lies between Badri gad and Barni gad in Yamuna valley region of the Garhwal Himalaya where a very large scal e investment is in the pipe line for Hydroelectric power generation.