Landslide hazards around Uttarkashi township, Garhwal Himalaya, after the tragic flash flood in June 2013
Garhwal Himalaya has witnessed extreme climatic conditions in the form of incessant rainfall during June 15–17, 2013, generating numerous primary as well as secondary landslide hazards due to flooding event in the Bhagirathi River. This was probably the second highest flood after the 1978 flood in the area. The paper documents the spatial distribution of landslides and its consequences in the lower reaches of the Bhagirathi Valley between Bhatwari and Uttarkashi. It has been observed that within a stretch of 28 km in the study area, the river gradient is highly variable ranging from 3.6 to 66.6 m/km and is marked by three major knick points. These knick points are well correlated with the disposition of thrusts and a fault present in the area. An inventory of 23 active landslides has been prepared. Based on these knick points, the entire area has been divided into four zones. The area between Bhatwari and Ganeshpur is marked by the zone of transportation and between Ganeshpur and Uttarkashi, the zone of deposition of river sediments. It has been estimated that there is an average aggradation of about 0.5 m/year in the Bhagirathi River around Uttarkashi. Further, the huge volume of material deposited in the river around Uttarkashi township is posing serious threat to the slope stability on either banks of river. This calls for an urgent need for the formulation of policy for dredging the material from riverbed in order to maintain the continuous and uninterrupted flow of water during high discharge, in order to mitigate the problems of slope stability along the course of the river.
KeywordsLandslides Flash flood Bhagirathi Valley Garhwal Himalaya
The authors thank the Director, Wadia Institute of Himalayan Geology, Dehradun, for providing all the necessary facilities to carry out the work. The work has been supported financially by the Department of Science and Technology (DST), Govt. of India “Map the neighbourhood of Uttarakhand” (MANU) scheme and the Norwegian funded NORSAR project. Research fellowship to Hemlata Nautiyal from the NORSAR project is thankfully acknowledged. We also thank Disaster Management Officer, Sh D. S. Petwal, Uttarkashi district, and Asst Engineer, Sh Mukesh Verma, Uttarakhand Jal Vidyut Nigam Limited (UJVNL), Maneri, Uttarkashi, for providing the discharge data and district administration Uttarkashi for providing the rainfall data of the area. Information provided by the local people about the damages caused by the flash flood was of immense help.
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