ICIMOD Study Warns of Rising GLOF Risks in Everest Region

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 flashpoints for glacial lake outburst floods (GLOFs), noting that the area has experienced five major events in less than 50 years.

The latest study, titled “Thame Valley Glacial Lake Outburst Flood – Causes, Impacts, and Future Risks,” examined the 2024 GLOF that devastated Thame village in Solukhumbu district on August 16, 2024. It found that a combination of geological and geomorphological factors amplified the flood’s destructive power, resulting in what ICIMOD described as a “devastating and complex chain reaction.”

According to the report, a rock avalanche struck a glacial lake at 4,900 metres, generating a powerful displacement wave that breached the lake’s moraine dam and released about 156,000 cubic metres of water. The outflow dropped 120 metres, increasing its erosive force before hitting a second lake. That lake’s dam also failed, creating a 22-metre-deep and 51-metre-wide breach and releasing another 303,000 cubic metres of water.

The combined waters transformed into a “hyper-concentrated flow of slurry,” sweeping debris and boulders nearly 80 kilometres downstream and eroding riverbanks along its path. The flood destroyed homes, a school, a health post, a bridge, and damaged a hydropower plant. However, no casualties were reported, largely because the event occurred during daylight and unfolded in stages.

The study’s authors — ICIMOD experts Sudan Bikash Maharjan, Tenzing Chogyal Sherpa, and Arun Bhakta Shrestha — said a natural narrowing of the river channel downstream of the Thyanbo outwash plain further intensified the flood’s erosive impact. The floodwaters eventually spread across the half-kilometre-wide valley floor near Thame.

According to ICIMOD, Nepal has recorded more than 90 GLOFs since the 1920s, with five significant events in the Everest region alone, including the 1985 Dig Tsho flood that destroyed a newly built hydropower plant.

“GLOFs are among the most destructive hazards in high-mountain regions,” the report warned. “They can release millions of cubic metres of water and debris within hours, devastating communities and reshaping landscapes.”

ICIMOD’s findings also underscore the growing impact of climate change on the Hindu Kush Himalaya (HKH) region, which is warming at an average of 0.28°C per decade — nearly three times the global rate. Glacier mass loss has surged by 65 percent in recent decades, resulting in the formation of more than 25,000 glacial lakes across the HKH, spanning the Amu Darya, Indus, Ganges, Brahmaputra, and Irrawaddy basins.

“Thame shows that we must devote much greater effort to understanding and mitigating risks even from smaller glacial lakes. The local geological and morphological features intensified the impact of this climate-driven event, though fortunately there was no loss of life,” said Maharjan.

Cryosphere analyst Sherpa noted that as climate extremes intensify, the Thame flood serves as a stark reminder of how mountain communities are already facing climate-induced disasters. “This event reinforces the urgent need to invest in preparedness, strengthen scientific understanding, and support those most at risk. The mountains are speaking; we just need to listen,” said Sherpa.

The report calls for immediate action in Thame, including protecting tension cracks from direct water flow, reinforcing riverbanks, and formulating a long-term flood risk management plan for the valley. It also stresses the urgency of expanding monitoring systems in high-altitude glaciated regions across the HKH.

Senior advisor Shrestha added, “The Thame case shows that glacial hazards are intensifying as the Hindu Kush Himalaya warms nearly three times faster than the global average. More hydrological and meteorological monitoring stations and engineering measures such as bank protection are essential to reduce future damages.” -- RSS