Glacial Lake Outburst Flood Hazard, Downstream Impact, and Risk Over the Indian Himalayas.

Indian Himalayas are home to numerous glacial lakes, which can pose serious threat to downstream communities and lead to catastrophic socioeconomic disasters in case of a glacial lake outburst flood (GLOF). This study first identified 329 glacial lakes of size greater than 0.05 km2 in the Indian Himalayas, and then a remote sensing‐based hazard and risk assessment was performed on these lakes. Different factors such as avalanche, rockfall, upstream GLOF, lake expansion, identification of the presence of ice cores, and assessment of the stability of moraine were considered for the hazard modeling. Further, a stochastic inundation model was applied to quantify the potential number of buildings, bridges, and hydropower systems that could be inundated by GLOF in each lake. Finally, the hazard parameters and downstream impact were collectively considered to determine the risk linked with each lake. A total of 23 lakes were identified as very high risk lakes and 50 as high‐risk lakes. The potential flood volumes associated with various triggering mechanisms were also measured and were used to identify the lakes with the most considerable risk, such as Shakho Cho and Khangchung Tso. This study is anticipated to support stakeholders and decision‐makers in identifying critical glacial lakes and make well‐informed decisions related to future modeling efforts, field studies, and risk mitigation measures. Key Points: Avalanche trajectories suggest that 36 out of 329 glacial lakes are susceptible to dynamic failure via an avalanche entering the lakeApplication of stochastic flood model reveals that 67 glacial lakes contain at least one hydropower system along their flow pathIndian Himalayas contain 23 critical glacial lakes, 17 of which are located in the state of Sikkim [ABSTRACT FROM AUTHOR]