Himalayan tsunami, not cloudburst behind 2023 Sikkim GLOF disaster: Study

Himalayan tsunami study reveals 2023 Sikkim flood details, warns of repeat disasters due to climate change impact.

GUWAHATI

A Himalayan tsunami generated by the collapse of a huge mass of rock, ice, and sediment into a glacial lake triggered the 2023 Sikkim flood that killed 55 people and destroyed a 1,200-megawatt hydropower dam on the Teesta River, a new study has revealed.

Also Read | What caused the flood in Sikkim? | Explained

The study by 34 scientists, members of NGOs, and other stakeholders from nine countries, published in the latest edition of the Science journal, did not rule out the possibility of repeat disasters but said there was no evidence that a cloudburst triggered the glacial lake outburst flood (GLOF). The Sikkim government attributed the GLOF to a cloudburst in its report to the National Green Tribunal in 2024.

The study’s lead author is Ashim Sattar, assistant professor at the School of Earth, Ocean, and Climate Sciences of the Indian Institute of Technology Bhubaneswar. Contributions included Praful Rao of the Kalimpong-based Save The Hills and Prabhakar Rai of the Sikkim State Disaster Management Authority.

The team said the study was carried out to understand the Sikkim disaster and identify major findings of wider relevance given rapid climate warming in mountain regions worldwide. It analysed the drivers, causes, and downstream impacts of the hazard cascade using high-resolution satellite imagery, seismic data, meteorological data, field observations, and numerical modelling to back-calculate the GLOF’s movement.

The study concluded that the disaster was triggered by the collapse of 14.7 million cubic metres of frozen lateral moraine into the South Lhonal Lake (SLL) at 5,200 metres above sea level in the Upper Teesta basin. The outcome was a 20-metre-high tsunami-like impact wave that rapidly created a major breach, releasing 50 million cubic metres of water, enough to fill about 20,000 Olympic-size swimming pools.