High-Mountain Hazards in the Indian Himalaya: An Assessment of the Causes and Effects of the Chamoli Flood in 2021

On 7 February 2021, a cascade of events severely impacted the mountainous river valleys in India’s northwestern District of Chamoli. A bedrock failure beneath a hanging glacier on Ronti Peak released an ice rock avalanche, which in turn resulted in a flood. Widespread devastation, complete destruction of two hydropower projects and more than 200 fatalities were the outcome. The purpose of this study was to assess some of the causes and effects of the flood. I used Planet© satellite imagery to assess potential causes and visualize the extent of the disaster. Using two high-resolution Digital Elevation Models (DEMs), I created a DEM of Difference Map (DoD) to calculate the ice rock avalanche detachment volume and to visualize surface changes in the affected area. In order to analyze the sources of the flood water, I gathered the mean temperature and compared it to the 30-Year Climate Normal. Further, I analyzed the precipitation recordings on the days prior to the flood to assess the origin of the flood water. My study revealed that the winter of 2020/2021 was warmer than average, yet the precipitation prior to the disaster seemed to have had minimal impact on the flood water source. The precipitation event did not significantly contribute to the flood water, but could have been a trigger of the bedrock failure, as it can take a few days for water to infiltrate through the ice and rock. The frequency and magnitude of natural hazards will most likely increase in the upcoming decades in response, but not limited to, weather patterns, environmental degradation and population growth. Hence, establishing an understanding of the physical processes but also taking into consideration the socio-environmental aspects in mountainous regions is crucial to prepare and decrease the risks of future hazards