Kedarnath disaster 2013: causes and consequences using remote sensing inputs

Kedarnath was devastated on 16th evening–17th morning (June 2013) due to landslides and flash floods that killed more than 5000 people in Uttarakhand. What really happened on 16th evening through next 12 h till final deluge on 17th morning has been a subject of speculation due to lack of sufficient eye witness and monitoring system. Earth observation techniques have provided information on precipitation, landslides, snow cover and other ancillary data such as digital elevation models at varying resolution. Using such spatial information along with limited eye witness and media reports, an attempt is made to reconstruct events that led to destruction in upper Mandakini valley with prime aim to improve response and minimise damage in the event of similar disaster in future. The study has revealed that there were two distinct events separated by a time gap of 10–12 h: the first event was triggered by series of landslides, river blockades, breaching, flooding and river bank failures, whereas the second event was mainly associated with Chorabari Tal Lake outburst flooding along with associated landslides and bank erosion. Comprehensive assessment of landslide hazard requires process-based modelling using numerical simulation methods. The present study aims to focus on analysis of landslides/debris flow movements and simulate landslides that occurred in Kedarnath event leading to derivation of important flow parameters to get closer to the root cause of the devastation. The unique geomorphological setting, which has changed significantly in the recent event, provides valuable inputs for critical assessment of damage and remedial measures in future. Comparison with Gohna Tal (in Birahi Ganga, a tributary of Alaknanda) landslide lake outburst flooding has provided closer insight on the event and it revealed how preparedness can reduce the impact of such natural disasters.