Looming tragedy: Sikkim lake that overflowed in 2023 was unstable for years, new study finds

A new paper on the 2023 Glacial Lake Outburst Flood that killed nearly 100 people in the northwestern part of Sikkim has revealed the magnitude of damage a GLOF can trigger.

- Jayashree Nandi

It also found that the surroundings of the South Lhonak lake have been unstable for a long time revealing that such an event was waiting to happen.

The paper, published in journal Science on Friday states that part of the lateral moraine that collapsed into the lake was unstable and was showing maximum displacement of more than 15 m per year between 2016 to 2023, years before the actual collapse.

"This finding shows that the surroundings of the South Lhonak Lake have been unstable now for a long time," the authors of the paper said in a statement.

"On 3 October 2023, a multihazard cascade in the Sikkim Himalaya, India, was triggered by 14.7 million m3 of frozen lateral moraine collapsing into South Lhonak Lake, generating a 20 m tsunami-like impact wave, breaching the moraine, and draining -50 million m3 of water," reads the abstract of the paper by 34 authors including climate scientists, geographers, geologists glaciologists, "The ensuing Glacial Lake Outburst Flood (GLOF) eroded -270 million m3 of sediment, which overwhelmed infrastructure, including hydropower installations along the Teesta River. The physical scale and human and economic impact of this event prompts urgent reflection on the role of climate change and human activities in exacerbating such disasters," it adds.