A massive rock and ice avalanche caused the 2021 disaster at Chamoli, Indian Himalaya

On 7 February 2021, a catastrophic mass flow descended the Ronti Gad, Rishiganga, and Dhauliganga valleys in Chamoli, Uttarakhand, India, causing widespread devastation and severely damaging two hydropower projects. More than 200 people were killed or are missing. Our analysis of satellite imagery, seismic records, numerical model results, and eyewitness videos reveals that similar to 27 x 10(6) cubic meters of rock and glacier ice collapsed from the steep north face of Ronti Peak. The rock and ice avalanche rapidly transformed into an extraordinarily large and mobile debris flow that transported boulders greater than 20 meters in diameter and scoured the valley walls up to 220 meters above the valley floor. The intersection of the hazard cascade with down-valley infrastructure resulted in a disaster, which highlights key questions about adequate monitoring and sustainable development in the Himalaya as well as other remote, high-mountain environments.

Automated summary

On February 7, 2021, a catastrophic mass flow hit the Ronti Gad, Rishiganga, and Dhauliganga valleys in Chamoli, Uttarakhand, India, causing extensive devastation and casualties. The collapse of rock and glacier ice led to a debris flow that transported large boulders and scoured valley walls, highlighting issues related to monitoring and sustainable development in high-mountain environments like the Himalayas.