Research identifies causes of catastrophic Sikkim flooding, calls for urgent action

By Jag Jivan  

A major international study involving a Newcastle University PhD student has pinpointed the causes of the devastating 2023 glacial lake outburst flood (GLOF) in Sikkim, India. The findings, published in Science, reveal how a combination of landslides and climate change led to the disaster while warning of growing risks in the Himalayas.  

Sonam Rinzin, a third-year PhD student in Newcastle University’s School of Geography, Politics, and Sociology, contributed to simulations that reconstructed the flood. The research team found that South Lhonak Lake, one of the region’s fastest-growing glacial lakes, collapsed after a massive landslide dumped 14.7 million cubic meters of debris into it. This triggered a 20-meter-high wave that breached the lake’s natural dam, releasing 50 million cubic meters of water—equivalent to 20,000 Olympic-sized swimming pools.  

The October 2023 disaster killed 55 people, left 74 missing, and caused destruction up to 385 kilometers downstream, affecting India’s Sikkim and West Bengal as well as Bangladesh. Heavy rainfall worsened the flooding by increasing landslide risks and sediment flow.  

The study, conducted by over 30 scientists from 10 countries, including experts from the Universities of Hull, Leeds, and Cambridge, highlights how climate change is accelerating glacier melt and increasing GLOF risks. Current hazard models often fail to account for cascading effects like landslides, leaving vulnerable communities at greater risk.  

Sonam Rinzin said, "This catastrophic event shows the urgent need for stronger early warning systems and policy changes to protect Himalayan communities. As an early-career scientist, I’m honored to have contributed to this vital research."  

Professor Dave Petley, Vice-Chancellor of the University of Hull and a lead researcher, warned, "Early warning systems and better risk management are essential, especially as hydropower projects expand in high-risk areas. Many developing nations face aid cuts, making this work even more urgent."  

Dr. Ashim Sattar from the Indian Institute of Technology Bhubaneswar, who led the study, stressed the need for improved modeling, regulations, and community preparedness to reduce future risks.  

Earlier research by Newcastle University identified High Mountain Asia, including parts of India, Pakistan, and China, as the world’s most GLOF-prone region, with 15.3 million people living near glacial lakes. The new study underscores the need for global action to address growing climate-related disasters in vulnerable mountain regions.