New Delhi, India – On the morning of August 26, the Himalayan landscape above Nepal’s Rasuwa district changed in minutes. A mass of ice and rock broke loose high in the mountains and sent a violent surge of water, mud and debris down the Lhende Khola River. The torrent travelled through valleys, swept away settlements and infrastructure and eventually reached the Nepal-China border. What followed was not simply a flood.
It was a chain reaction. By mid-September, more than 1,400 people had been reported dead and at least 6,000 remained missing in Nepal and across the border in Tibet. Twelve hydropower plants were destroyed, while roads, bridges and homes were buried or washed away. The scale of the destruction has left scientists and disaster managers confronting a difficult question: How do you warn communities about a disaster whose trigger may occur high above them, in terrain that is difficult to monitor and where there may be only minutes to react?
Basanta Raj Adhikari, director of the Centre for Disaster Studies at Tribhuvan University in Kathmandu, described the event to Al Jazeera as unprecedented in size, affected area and mechanism. His estimate suggested that the energy involved was greater than that released by the Hiroshima atomic bomb, a comparison intended to illustrate the scale of the physical forces involved rather than suggest that the event was equivalent to a nuclear explosion. For scientists who study the Himalayas, the disaster demonstrated how quickly an event originating in a remote, high-altitude environment can become a regional catastrophe. And Nepal is not alone.
A warming climate is altering glaciers, snow cover, permafrost and high-altitude lakes. At the same time, roads, hydropower projects, tourist facilities and settlements have pushed deeper into mountain valleys. That combination is creating a new risk landscape in which one hazard can trigger another. An avalanche can block a river.
A blocked river can form a temporary lake. A sudden release can become a debris flow. That debris can destroy a road or bridge, block another river and create another flood downstream. The August disaster in Nepal showed how quickly such a sequence can unfold.
It also exposed a weakness in the way early-warning systems are often designed. Many systems are built around a particular hazard: rainfall, river level or glacial lake outburst flood. But the Himalayas do not always respect those categories. In July, the International Centre for Integrated Mountain Development, or ICIMOD, warned that a below-normal monsoon should not be interpreted as a safer one. “The biggest misunderstanding is that less seasonal rainfall means lower flood risk,” said Saswata Sanyal, a disaster risk reduction specialist at ICIMOD. “A drier monsoon can still be a dangerous monsoon,” he added, warning that seasonal averages cannot capture the cloudbursts capable of producing catastrophic flooding in mountain valleys.
The Nepal disaster went a step further. The immediate trigger was not simply heavy rainfall. Scientists have been examining an ice-rock avalanche and other possible processes that temporarily obstructed the river system before releasing a destructive surge. ICIMOD has described the event as an ice avalanche rather than a conventional glacial lake outburst flood, while other scientists have examined the role of local seismic activity and other high-altitude processes.
A warning system waiting for rainfall or a rising river may not provide enough time when the real trigger happens several kilometres upstream and above the line of sight of the communities below. Thousands of kilometres away, scientists studying Kashmir’s Himalayas are seeing another part of the same problem. A study published in the Journal of Glaciology this year mapped 155 glacial lakes above 2,500 metres (8,200ft) across the Himalayas in Indian-administered Kashmir. The researchers found that the area of ice-contact proglacial lakes – bodies of water that form directly against the margin of a melting glacier, trapped by moraine ridges, bedrock basins, or ice dams – had increased by 26 percent between 1992 and 2024.
Five lakes were classified as having very high susceptibility to glacial lake outburst floods. An outburst from those lakes, the researchers found, could threaten several thousand buildings, 15 major bridges, roads and a hydropower project. More significantly, the study warned that hazards could occur in chains, with an upstream lake outburst potentially triggering secondary events downstream. For Irfan Rashid, a glaciologist and associate professor at the University of Kashmir who co-authored the study, the implications extend beyond individual lakes.
Rashid recently told Al Jazeera that without action, the melting, thinning, and destabilisation of glaciers, seasonal snow cover, and permafrost along the Hindu Kush-Himalayas system would increase, and water shortages could become a major problem across the Upper Indus, Ganga and Brahmaputra basins by the end of the century. That is why the Nepal disaster resonates in Kashmir. The landscapes are different, the rivers are different and the individual hazards may differ. But the underlying problem is increasingly similar: Communities living downstream of a rapidly changing high-altitude environment may have little time to respond when something breaks loose above them.
The challenge is particularly acute in places where roads, bridges and hydropower projects occupy narrow valleys. Once a mountain river begins carrying enormous quantities of rock, ice and mud, infrastructure designed for conventional floods can quickly become irrelevant. The same concern runs across the western Himalayas and Karakoram ranges. The Gilgit-Baltistan region in Pakistan-administered Kashmir contains hundreds of glaciers and glacial lakes, while communities and infrastructure sit along valleys exposed to sudden floods and landslides.
Pakistan has responded by expanding early-warning infrastructure. Under a United Nations-supported programme, early-warning systems, evacuation shelters, disaster-management centres and other protective measures have been established in vulnerable valleys. But technology alone cannot solve the problem. A sensor can detect a change.
Someone still has to receive the message. Someone has to understand what it means. And people downstream have to have a route to safety. That last part is often the weakest link.
A siren is useful only if the people hearing it know where to go. An automatic warning is useful only if it arrives before the flood. A satellite image is useful only if the information can be converted into a decision quickly enough to save lives. This is why disaster scientists increasingly talk about anticipatory action rather than simply disaster response. “The era of preparing for a single, predictable hazard is over,” Sanyal said earlier this year. “Anticipatory action and early warning must now be the foundation.” The Himalayas are also becoming more heavily engineered.
Hydropower is central to Nepal’s economy. Roads are being expanded. Border crossings are growing in importance. Tourism is pushing deeper into remote valleys.
The benefits are obvious. So are the risks. The August disaster struck an area where hydropower infrastructure was concentrated along the river corridor. At least 900 workers were believed to have been inside tunnels and other facilities in the aftermath, making rescue operations extraordinarily difficult.
Two workers were eventually pulled alive from a hydropower tunnel nine days after the disaster. The question is no longer simply whether infrastructure can withstand a flood. It is whether planners have adequately considered what happens when a flood is carrying an enormous mass of rock and ice, when a river changes course, or when one mountain hazard triggers another. For decades, engineering risk assessments have often relied on historical records.
But history becomes a less reliable guide when the physical conditions producing disasters are changing. A river that flooded once every several decades may no longer behave according to the same pattern. A glacier that appeared stable from satellite imagery may sit beneath an increasingly unstable slope. A lake that was considered remote may suddenly become a threat to a road, village or power plant hundreds of metres below.
There is another complication that no satellite can solve on its own. The Himalayas are divided among countries with different political systems, security concerns and approaches to sharing information. But rivers do not stop at international boundaries. Neither do floods.
The August disaster reached the Nepal-China border and damaged the Gyirong crossing, an important trade and pilgrimage route. The disaster also raised questions about how quickly information about hazards in high mountain areas can move between countries. This is where regional cooperation becomes more than a diplomatic slogan, experts say. A sensor positioned in one country can provide warning to people in another.
A satellite image collected over one mountain range can reveal a developing hazard that threatens a valley downstream. A river gauge can provide critical information before floodwaters reach a settlement. The technical capability already exists in many cases. The missing piece is often the architecture connecting it.
A 2026 assessment of Himalayan disaster risks has argued for stronger monitoring, early-warning systems and regional coordination because hazards are increasingly interconnected. The idea is simple: Information about a mountain hazard should not stop at the same line where a political boundary begins. The August disaster in Nepal isn’t a tragedy belonging to one country, point out experts. The Kashmir Himalayas study has already identified lakes capable of producing destructive outburst floods and has warned of cascading processes.
Northeast India’s Sikkim provides another example. After the 2023 South Lhonak glacial lake outburst flood killed dozens and damaged major infrastructure, India expanded monitoring and mitigation efforts. Today, 40 high-risk glacial lakes have been identified in Sikkim, including 16 placed in the highest-risk category, with authorities working on drainage, flood-retention and other protective measures. But the lesson from each disaster is broadly the same: Waiting for a disaster to prove the risk is the most expensive form of preparedness.
The Himalayas are sometimes called the Third Pole because they contain one of the world’s largest concentrations of snow and ice outside the Arctic and Antarctic. Major Asian rivers depend on water originating in these mountains. Hundreds of millions of people live downstream. That makes the changing Himalayas not only an environmental issue but a security, infrastructure and humanitarian one.
The August disaster demonstrated the most frightening version of that future. A mountain can collapse without warning. A river can become a weapon of debris. A hydropower tunnel can become a trap.
A border crossing can disappear in minutes. And by the time people downstream understand what is happening, the water may already be there. It’s a future that a region stretching from northeast India, spanning Tibet, Nepal, Kashmir and Pakistan, can no longer ignore. Yet disaster management remains largely divided by national boundaries.
That contradiction is becoming harder to navigate. The next glacial collapse could begin in Kashmir. It could begin in Pakistan’s high mountains. It could begin in Sikkim, Nepal or Tibet.
Wherever it starts, the same question will follow the mountain downstream: Who knew, how early did they know, and did the warning reach the people in time? For a region entering an era of increasingly complex mountain hazards, that may be the real measure of whether the Third Pole is prepared.
