Kathmandu: A recent study conducted by the International Centre for Integrated Mountain Development (ICIMOD) has identified the Dudh Koshi river basin and the Everest region as a critical flashpoint for glacial lake outburst floods (GLOFs). The region, which has experienced five significant GLOFs in less than half a century, continues to pose a substantial threat to downstream communities.
According to National News Agency Nepal, the ICIMOD study focused on the 2024 GLOF event in the Everest region, revealing a ‘devastating, and complex, chain reaction’ of geological and geomorphological factors. These factors significantly amplified the destructive power of the flood that devastated the high-altitude trekking village of Thame in Nepal’s Solokhumbu district on August 16, 2024.
The report details how the outflow of water descended 120 meters, increasing its erosive power. It then impacted a second lake, which breached its moraine dam, creating a massive hole and releasing an additional 303,000 cubic meters of water. This resulted in a ‘hyper-concentrated flow of slurry’ that traveled 80 kilometers downstream, causing extensive erosion and transporting debris, including large boulders.
The study underscores the growing severity of GLOFs across the Hindu Kush Himalayas, driven by rising temperatures that have increased the number of glacial lakes to 25,000 across the region. The report, titled ‘Thame Valley Glacial Lake Outburst Flood – Causes, Impacts, and Future Risks,’ highlights the urgent need for proactive risk management and mitigation strategies.
Risk experts at ICIMOD, including Sudan Bikash Maharjan, Tenzing Chogyal Sherpa, and Arun Bhakta Shrestha, co-authored the report. They confirmed that a rock avalanche triggered a powerful displacement wave, breaching a glacial lake at 4,900 meters and releasing 156,000 cubic meters of water. This event caused extensive destruction, including damage to homes, a school, a health post, a bridge, and a hydropower plant. Fortunately, due to the flood’s occurrence during daylight and its phased nature, there was no loss of life.
Nepal has experienced over 90 GLOFs since the early 1920s, with the Everest region enduring five significant events in less than 50 years. Among these was the 1985 GLOF of Dig Tsho, which destroyed a hydropower plant in a neighboring valley.
ICIMOD experts emphasize the accelerating impacts of climate change in the Hindu Kush Himalaya region, which is warming at an average of 0.28 degrees Celsius per decade. This warming has led to unprecedented glacier mass loss, fueling the proliferation of over 25,000 glacial lakes across the region’s major river basins.
Remote sensing analyst Maharjan stated, “The Hindu Kush Himalayas has more than 25,000 glacial lakes, and Thame shows us that we need to spend much more effort in understanding and preventing the risks posed by even the relatively smaller lakes.” Meanwhile, cryosphere analyst Sherpa highlighted the need for investment in preparedness and resilience, in line with this year’s International Day for Disaster Risk Reduction theme.
The study calls for specific actions in Thame, including protecting tension cracks, supporting riverbanks, and developing a long-term flood risk management plan. It also emphasizes the urgency of enhancing monitoring of high-altitude glaciated regions across the Hindu Kush Himalayas.
Senior advisor Shrestha noted, “The Thame case shows the glacial hazards are intensifying as the Hindu Kush Himalaya warms nearly three times faster than the global average. This highlights the need for more hydrological and meteorological monitoring stations and engineering measures to reduce future damages.”