Nepal floods underscore rising glacier risks in warming Himalayas

The deadly flash flood that swept through parts of Nepal on Wednesday was likely triggered by a massive section of glacier breaking away and temporarily blocking a river, causing a sudden surge of water downstream, scientists said.

Researchers are still examining satellite images and ground data to determine exactly how the disaster unfolded. The flood killed hundreds of people and left many others missing, including foreign nationals and pilgrims.

The US Geological Survey identified the event as a magnitude 5.2 glacier collapse that sent ice, rock and debris downstream with devastating force.

Jakob Steiner, a geoscientist at Austria's University of Graz, said satellite imagery indicated that a large lower section of the glacier had broken away and fallen.

Scientists cautioned against directly linking the disaster to climate change at this stage. However, they said rising global temperatures are altering the Hindu Kush Himalaya region and increasing the likelihood of dangerous glacier-related events.

Saswat Sanyal, a disaster risk reduction specialist at the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, said rising temperatures are causing significant changes in the region and accelerating glacier melt.

Sudden surge left little time to escape

Researchers said water levels in some rivers rose by as much as 9 metres within 30 minutes following the glacier collapse.

Preliminary findings suggest a large amount of ice and rock fell into the Lhende Khola, a tributary of the Bhote Koshi River. The collapse may have displaced water and swept up loose sediment and boulders, creating a powerful debris flow.

Scientists are also investigating whether the falling material temporarily blocked the river, allowing water to accumulate before the blockage gave way and intensified the downstream flood.

The affected area has experienced other major mountain disasters. A glacial lake flood struck the same valley in 2025, while an ice and rock avalanche hit another part of the region in 2024.

Warming increases glacier-related hazards

The Hindu Kush Himalaya is warming rapidly, causing major changes to glaciers, snow cover, permafrost and mountain slopes.

The region contains more than 63,000 glaciers that supply water to at least 10 major Asian river systems and support the food, water and energy needs of billions of people.

Scientists say about 78% of the glacier area between 4,500 and 6,000 metres above sea level is highly exposed to warming.

Research by ICIMOD has found that glacier melt across the region has accelerated, with ice-loss rates doubling since 2000.

As glaciers retreat, melting ice can enlarge glacial lakes and increase the risk of sudden floods. The loss of ice support can also expose mountain rock to warmer temperatures, rainfall and repeated freezing and thawing, making slopes less stable.

Experts warn that a single glacier collapse or avalanche can trigger a chain of events involving debris flows, river blockages and devastating flash floods.

Early warning systems crucial

Scientists said the latest disaster highlights the need for stronger monitoring and early warning systems across the Himalayas.

Steiner said about 10% of Nepal's power generation capacity is located in the affected valley, underscoring the risks to critical infrastructure.

With more than a million tourists visiting Nepal annually in recent years, experts said warning systems should protect both local communities and visitors.

However, monitoring thousands of glaciers, steep slopes and river valleys across the Himalayas remains extremely difficult.

Sanyal said authorities may have only a few minutes to respond once a chain of mountain hazards begins.

Experts called for stronger early warning systems, improved monitoring and faster information sharing among countries in the Himalayan region as climate change continues to make mountain environments increasingly unstable.