Study of Landslide Hazard Zonation in Mandakini Valley, Rudraprayag District, Uttarakhand Using Remote Sensing and GIS

The Mandakini Valley of Rudraprayag district, Uttarakhand witnessed unprecedented damage to life, property, infrastructure and landscape on 16 and 17 June 2013 due to torrential rains. Run-off discharge data indicate that antecedent rainfall exceeded the limit and the overflow of rivers led to landslide in the region and flash floods in the downstream areas. Fragile geology of the area, close to Main Central Thrust (MCT), degradation processes and torrential rains are responsible for triggering landslides and flash floods. A landslide inventory was carried out in the affected areas based on pre- and post-flood high resolution satellite data (LISS-IV and Cartosat-2). A total of 290 landslides were identified from pre-flood satellite LISS IV (2011) imagery and 1665 were identified in post-flood satellite imagery along major rivers. Using remote sensing and geographic information system techniques, thematic layers were generated. Using the weightage rating system, a landslide hazard zonation map of the area was prepared. Each class within a thematic layer was assigned an ordinal rating from 1 to 9. Summation of these attribute values was then multiplied by the corresponding weights to yield different zones of landslide hazard. A landslide hazard zonation map having five different zones ranging from very low hazard zone to very high hazard zone was prepared with the objective to create a reliable database for post-disaster management and for planning developmental activities in the district.