Study calls for urgent action as glacial lake outburst floods rise across the Himalayas.

A new study released by the International Centre for Integrated Mountain Development (ICIMOD) has confirmed that the devastating 2024 Thame flood in Nepal’s Everest region was triggered by a massive rock avalanche that set off a complex chain reaction of glacial lake outburst events. The study warns that the Everest region is emerging as a “hotspot” of cryosphere-linked hazards, with climate change amplifying both the frequency and magnitude of such disasters.

The report, Thame Valley Glacial Lake Outburst Flood – Causes, Impacts, and Future Risks, authored by ICIMOD scientists Sudan Bikash Maharjan, Tenzing Chogyal Sherpa, and Arun Bhakta Shrestha, reconstructs the catastrophic event of 16 August 2024, when a rock avalanche above 4,900 metres slammed into a glacial lake in the Thame watershed. The impact displaced around 156,000 cubic metres of water, unleashing a destructive cascade that tore through the iconic trekking village of Thame in Solukhumbu, displacing 135 people, destroying 25 homes, and devastating local infrastructure.

The avalanche’s impact generated a powerful displacement wave that breached a second downstream glacial lake, releasing an additional 303,000 cubic metres of water – a combined total equivalent to 185 Olympic-sized swimming pools. As the outflow plunged 120 metres between lakes, it gained immense erosive energy, transforming into a hyper-concentrated slurry that carried large boulders and debris up to 80 kilometres downstream.

“The Thame flood was not a single event but a devastating chain reaction driven by geological and morphological conditions,” said Sudan Bikash Maharjan, Remote Sensing Analyst at ICIMOD. “It shows how smaller glacial lakes – when coupled with unstable mountain slopes – can unleash catastrophic impacts.”

A Warning from the Mountains

The flood destroyed homes, a health post, a school, a bridge, and damaged a hydropower plant. Fortunately, no lives were lost, as the flood occurred during daylight and unfolded in phases due to temporary ponding of the water. But the destruction underscored the growing vulnerability of Himalayan communities to climate-driven disasters.

The Thame incident joins a troubling pattern: the Everest region has experienced five major glacial lake outburst floods (GLOFs) in less than 50 years, including the 1985 Dig Tsho disaster, which destroyed a hydropower plant in a nearby valley. Across Nepal, more than 90 GLOFs have been recorded since the early 20th century.

“Thame is both a reminder and a moment of reflection,” said Tenzing Chogyal Sherpa, Cryosphere Analyst at ICIMOD. “It shows how mountain communities are already living the realities of climate change. We must invest urgently in preparedness and resilience, especially as the mountains continue to speak through such events.”

Cryosphere Under Threat

The study situates the Thame disaster within the larger context of the Hindu Kush Himalaya (HKH) – one of the most climate-sensitive mountain regions on Earth. The HKH is warming at an alarming rate of 0.28°C per decade, nearly three times the global average. This rapid warming has accelerated glacier melt, leading to a 65% increase in glacier mass loss in recent decades and a surge in the formation of glacial lakes – now numbering over 25,000 across the region.

“These lakes are ticking time bombs,” warned Arun Bhakta Shrestha, Senior Advisor at ICIMOD and co-author of the report. “In the last two years alone, several high-altitude hazards, including GLOFs, have struck the region. We urgently need more hydrological monitoring stations and engineering interventions such as riverbank reinforcements to mitigate future damages.”

The study notes that the Dudh Koshi River basin, home to the Thame and Dig Tsho lakes, is particularly vulnerable due to its steep topography, moraine-dammed lakes, and active geological conditions. Natural narrowing of river channels, such as the one below Thyanbo outwash plain, can further intensify erosion and debris flow, as seen during the 2024 flood.

Call for Proactive Risk Management

ICIMOD’s researchers emphasize that proactive risk management – rather than reactive recovery – must become the cornerstone of Nepal’s mountain hazard response. Their recommendations include:

• Protecting tension cracks from direct water infiltration to prevent slope failure.
• Reinforcing riverbanks to reduce subsidence and erosion.
• Developing long-term flood risk management plans for high-risk valleys like Thame.
• Expanding real-time monitoring of high-altitude glacial systems across the HKH.

The study was launched in Kathmandu during an event marking the International Day for Disaster Risk Reduction (IDDRR), co-hosted by Nepal’s National Disaster Risk Reduction and Management Authority (NDRRMA), Disaster Preparedness Network-Nepal (DPNet-Nepal), and ICIMOD. Conducted with support from the Asian Development Bank, BGC Engineering, and Solukhumbu District Administration, the research combined satellite imagery, drone surveys, and on-site geomorphological assessments to reconstruct the flood’s sequence. Drone footage provided by the Sagarmatha Pollution Control Committee was instrumental in mapping the debris path and quantifying the damage.

Mountains in Crisis

The Thame flood, experts say, is part of a growing global concern about the fragility of high-mountain cryospheres under climate stress. With glaciers retreating rapidly, the risk of cascading hazards – where avalanches, landslides, and GLOFs trigger one another – is increasing. Such chain reactions threaten not only remote Himalayan villages but also major river systems that sustain over a billion people downstream.

Projects like ICIMOD’s Building Adaptation and Resilience in the Hindu Kush Himalayas (BARHKH) initiative are now working to help governments integrate cryosphere science into national policies and prioritize climate-resilient infrastructure investments.

As Sherpa put it, “Events like Thame remind us that the cryosphere is not a distant concern. What happens in the mountains reverberates downstream and across borders. The time to act is now – because these are not isolated disasters, but the voice of a changing planet.”