Produced by: Tarun Mishra
Designed by: Mohsin Shaikh
A glacial lake outburst flood (GLOF) is a sudden and destructive flood resulting from the failure of a dam containing a glacial lake. It can occur due to various factors, including climate change, permafrost melting, or geological activities
The increasing melting of glaciers due to climate change has raised concerns about the heightened risk of GLOFs. This threat is particularly significant in regions with active geologies, such as the Himalayas
A 2023 study has identified approximately 15 million people at risk from GLOFs, primarily in China, India, Pakistan, and Peru. These regions are susceptible to the devastating consequences of glacial lake outburst floods
GLOFs can occur when water is dammed by a glacier (marginal lake) or is capped by the glacier itself (sub-glacial lake). The release of water from these dams can lead to outburst of floods
The recent flash flood in Sikkim, India, was primarily sourced from the South Lhonak glacial lake, situated in the Upper Teesta Basin. This glacial lake had expanded significantly due to increased ice melt
In the early hours of the disaster, an intense cloudburst led to the rapid filling of the South Lhonak lake. The resulting collapse of the lake unleashed a deluge that devastated buildings, bridges, and communities
Credit: Twitter
The flash flood also had a severe impact on the Teesta Stage III Hydro Electric Project's Chungthang dam, which was constructed in 2017 and is the largest hydropower project in Sikkim
The floods swept away houses, buildings, and infrastructure along the Teesta River and Lachen Valley, rendering several areas inaccessible. Communication networks were disrupted, and highways and bridges collapsed
The floods' seismic signals were detected as far away as Kathmandu. While initial concerns focused on a 5.7 magnitude earthquake in Nepal, satellite data suggests that extreme cloudburst triggered the GLOF event
Nepal has actively implemented measures to reduce GLOF-related casualties, including draining growing lakes and identifying risk levels associated with glacial lakes
Peru has been proactive in monitoring glacial lakes and establishing early warning systems following a devastating GLOF event in 1941, which resulted in significant casualties
India has approached GLOF events as part of earthquake mitigation efforts, utilising satellite observations to identify glacial lakes requiring drainage. Ironically, earlier this year, scientists were exploring glacial lake draining in Sikkim to address the looming threat of GLOFs
The toll in the flash flood in Sikkim mounted to 21 on Friday as Army and NDRF teams worked their way through slushy earth and fast flowing water in the Teesta river basin and downstream north Bengal for the third day in search of those who were swept away and are still missing