Satellites reveal cause of Chamoli disaster

On 7 February 2021, the Chamoli district in the Uttarakhand region of India experienced a humanitarian tragedy when a large mass of rock and ice, around 27 million cubic metres, was released from the steep mountain flank of the Ronti peak.

This collapse caused a flow of debris to barrel down the Ronti Gad, Rishiganga, and Dhauliganga river valleys, causing significant destruction along the route, killing more than 200 people and destroying two major hydropower facilities that were under construction.

Lead author Dan Shugar, Associate Professor in the Department of Geoscience at the University of Calgary, commented, “The rapid increase in the number of satellites orbiting Earth allowed our team to understand the basics of what happened in a matter of hours. We now have access to satellites that image every part of Earth every day – sometimes even multiple times per day – and this has really revolutionised how we do this sort of science.”

The results of the analysis were also sent to the governmental agencies of India to help them plan and support emergency assistance to the local teams.

Two participants from ESA’s Climate Change Initiative, specifically the Glaciers_cci and Permafrost_cci projects, helped with the retrieval and analysis of satellite images which included Copernicus Sentinel-2, PlanetLab and Corona.

Andreas Kääb, from the University of Oslo, was able to determine the volume and ice/rock mixing ratios based on his experience with such events from earlier studies. He explains, “The calculated 80% rock in the avalanche completely converted the 20% glacier ice into water over the 3200 m elevation difference from Ronti Peak to the Tapovan hydropower plant. This conversion is largely responsible for the devastating impact of the resulting mud and debris flood wave.”