Study Identifies Causes of Devastating Sikkim Flood in 2023

28 March 2025 – A global investigation has pinpointed the main causes of the devastating Sikkim flood in 2023. A Newcastle University PhD student was among the team who studied why the glacial lake outburst flood (GLOF) caused so much destruction in the area.

The research, conducted and published in Science, had studied the South Lhonak Lake GLOF in Sikkim's Upper Teesta basin at 5,200 meters. The glacial lake, one of the largest and fastest-developing in the Himalayas, is a cause of concern due to the increasing likelihood of GLOFs. The lake burst on 3 and 4 October 2023, inundating and killing 55 individuals, leaving 74 missing and damaging infrastructure, including the Teesta-III hydropower dam. Scientists discovered that a landslide had dumped 14.7 million cubic meters of frozen material into the lake, creating a 20-meter-high wave. The wave crested the moraine dam, discharging an estimated 50 million cubic meters of water—the equivalent of 20,000 Olympic-sized swimming pools. The flood traveled downstream and devastated as much as 385 km downstream, not just in Sikkim but also in West Bengal and Bangladesh.

The research was conducted through numerical modeling and before-and-after-event data analysis to examine the role of the landslide, heavy rain, and sedimentation in causing the disaster. It emphasized the growing dangers from climate change, which speeds up glacier melting and increases the frequency of such high-end events. The results also indicated shortcomings in existing GLOF models, which do not account for erosion, sediment transport, and cascading processes. This risk underestimation calls for enhanced early warning systems and enhanced policy interventions to safeguard individuals in high-altitude areas.

The study was conducted by researchers from ten nations, among them researchers from the UK universities of Hull, Leeds, and Cambridge, in addition to India and Bangladesh's institutions and non-government organizations. The researchers emphasized improving GLOF hazard assessments, regulatory frameworks, and neighborhood-based awareness programs. A previous global analysis of GLOF-risk areas by Newcastle University in February 2023 showed that 15.3 million individuals globally reside within 50 km of a glacial lake. The greatest risks were found in High Mountain Asia, spanning terrain in India, Pakistan, and the Tibetan Plateau.

The research underscores the necessity of incorporating early warning systems, risk management policies, and sustainable development measures in the susceptible areas by governments and policymakers. The research is a step towards crucially fulfilling how and why the increased risk of GLOFs in the Himalayas can be understood and avoided.

Source and Credits:
Source: Newcastle University, Science Journal