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 ~27 × 10⁶ 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 downvalley 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.

2021 年 2 月 7 日，一场灾难性的水流从印度北阿坎德邦 Chamoli 的 Ronti Gad、Rishiganga 和 Dhauliganga 山谷下降，造成大面积破坏并严重破坏了两个水电项目。超过200人死亡或失踪。我们对卫星图像、地震记录、数值模型结果和目击者视频的分析表明，~27 × 10 ⁶立方米的岩石和冰川冰从 Ronti Peak 陡峭的北面崩塌。岩崩和冰崩迅速转化为异常巨大的流动泥石流，运送直径超过20米的巨石，冲刷到谷底220米处的谷壁。灾害级联与下游基础设施的交叉导致了一场灾难，这凸显了有关喜马拉雅山以及其他偏远高山环境的充分监测和可持续发展的关键问题。