28th of March 2025 : As a member of an international team of experts, Sonam Rinzin, a third-year PhD student from the School of Geography, Politics, and Sociology, contributed to an in-depth study on the devastating effects of a glacial lake outburst flood (GLOF). These floods occur when meltwater, held back by moraine or ice dams left behind as glaciers recede, suddenly bursts through. Such events can cause extensive damage to property, infrastructure, and agricultural land, posing a significant risk to human life. The sequence of events that occurred during the Sikkim flood in 2023 was simulated by Sonam. The impact of mass moraine failure entering the lake, its interaction with lake water, and the resulting formation of impulse waves, and moraine dam failure were all examined. Pre- and post-event data as well as numerical modelling served as the foundation for these simulations.
As melting glaciers continue to increase the risk of GLOFs in the Himalaya region, the team’s findings, which were published in Science, highlight the urgent need to strengthen prediction and early warning systems as well as GLOF hazard assessments.
Sonam stated, “
The 2023 catastrophic GLOF event of Sikkim left enormous destruction and damage downstream and is an example of how hazardous glacial lakes can be for communities in the Himalaya.This novel scientific effort, which investigated the intricate causes, dynamics, and consequences of this catastrophic flood cascade is enormously important, not only for understanding the cause and consequences of the event itself, but also for highlighting the urgent need for collaborative efforts to reduce and mitigate GLOF risk in the Himalaya. As an early-career scientist, I feel privileged to have contributed to this significant research and to have collaborated with over 30 scientists from 10 countries. This experience provided me with a valuable opportunity to interact with some of the world’s leading scientists while also enhancing my academic and technical skills.”.
The source of the 2023 flood, South Lhonak Lake, is located in Sikkim’s Upper Teesta basin in northeastern India at 5,200 meters above sea level. Being one of the biggest and fastest-growing glacial lakes in the area, it presents serious risks because of the possibility of GLOFs. On October 3 and 4, 2023, these risks came to pass as the lake erupted catastrophically, causing a flood cascade that killed 55 people, left 74 missing, and devastated most of the area downstream, including the Teesta-III hydropower dam.
The results showed that the outburst was caused by a landslip that deposited 14.7 million cubic meters of frozen debris into South Lhonak Lake. The consequent 20-meter tsunami-like wave broke through and undermined the frontal moraine that held the lake’s water, releasing about 50 million m3, or 20,000 Olympic-sized swimming pools. Infrastructure downstream suffered significant damage as a result of the massive amount of water that flowed down the valley. As heavy rainfall primed the landscape for landslides and compounded sediment transport and downstream destruction in the Teesta Valley, the research team, which included scientists from ten countries, including the universities of Hull, Leeds, and Cambridge in the UK, as well as non-governmental organisations and other stakeholders in India and Bangladesh, demonstrated how climate change exacerbated the event. This hit Bangladesh as well as Sikkim and West Bengal in India, causing infrastructural destruction up to 385 km from the flood’s source.
The findings, according to the authors, highlight the shortcomings of current GLOF models, which frequently neglect to take erosion, sediment transport, and cascading processes into account. They also emphasise the necessity of improved early warning systems, policy changes, and adaptive risk management techniques, especially in remote, high-altitude, vulnerable glacial regions like the Himalayas.
Professor Dave Petley, Vice-Chancellor of the University of Hull and a leading expert in landslide research and management served as the UK lead for the international collaboration. He stated: “This research underscores the critical need for early warning systems, effective risk management strategies, and further research to assess the threats posed by the increasing number of hydropower projects in the region. The urgency of this work cannot be overstated, particularly as many developing countries are now facing cuts in aid. Gaining a clear understanding of what transpired is essential for identifying future risks and ensuring better protection for vulnerable communities.”
Dr. Ashim Sattar, an assistant professor at the Indian Institute of Technology, Bhubaneswar, led the study. He explained, “It is evident that an integrated approach is required to reduce the risks of GLOFs in the Himalayas, including early warning systems, strengthened regulatory frameworks, a paradigm shift in GLOF modeling approaches, and robust preparation programs and community education.”
A team led by Newcastle University created the first worldwide evaluation of GLOF-risk areas in February 2023 and determined priority areas for mitigation. The study found that 15.3 million people reside within 50 km of a glacial lake and that the largest GLOF hazard is found in High Mountain Asia, which includes parts of India and Pakistan as well as the Tibetan Plateau, which stretches from Kyrgyzstan to China.
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