KATHMANDU, Sept 6: The Bhotekoshi flood has left behind one of the most complex humanitarian disasters in Nepal’s history. It was not simply a flood triggered by heavy rainfall. Instead, a massive ice-and-rock avalanche blocked the Lhende River in Tibet, forming a temporary lake that suddenly burst and sent a devastating surge downstream.
But as the scale of the destruction becomes clearer, a difficult question remains: Was this simply a natural disaster, or was the devastation also a consequence of the state’s lack of preparedness?
At first, many people assumed they were witnessing another major monsoon flood. Experts, however, say what happened was far more unusual — and far more dangerous.
Satellite analysis shows that a massive mass of ice and rock, nearly 600 meters wide, broke away from the lower section of a glacier located about 15 kilometers west of Langtang Lirung and swept downstream.
Geologist Prakash Pokharel said the ice-rock avalanche carried huge amounts of mud, stones and ice into the river, turning the Bhotekoshi and Trishuli rivers into raging torrents.
Chinese researchers add that, as the flood travelled through a 22-kilometer gorge, it picked up more soil, rocks and large trees, transforming what might otherwise have been a flood into something resembling a “Himalayan tsunami.”
According to the Flood Forecasting Division (FFD), the disaster was part of a chain of risks in which snow or a landslide blocks a river, a temporary lake forms and the lake suddenly bursts — a scenario that falls outside Nepal’s traditional rainfall-based forecasting system.
Climatologist Dr Dharam Raj Uprety said rising temperatures are weakening the snow that has remained firmly packed in the Himalayan region, increasing the likelihood of such events.
A warning that came too late
More than 60 percent of the Bhotekoshi watershed lies in China. Although Nepal and China agreed to exchange information in real time following the 2025 flood, no formal agreement or automated communication system had been established.
As a result, Nepali officials learned that a river had been blocked in China and that the temporary lake had burst only nearly five hours after the incident — and even then through unofficial channels.
The delay left authorities with virtually no time to alert downstream communities.
According to flood experts, Nepal’s flood forecasting system is primarily based on rainfall and river water-level measurements. But because this flood was triggered by the bursting of a temporary lake formed after an ice-rock avalanche, there were no gradual signs of rising water levels.
Instead, the flood arrived suddenly, travelling at a speed of 15 to 20 meters per second.
Bhotekoshi disaster raises questions over speed and scale of re...
An official at the FFD said automatic water-level sensors installed about 10 meters above the riverbanks were swept away before they could send any warning signals.
At around 8:50 am, the Syabrubesi water-level monitoring station, located several kilometers downstream from the Rasuwagadhi border point, stopped transmitting data. There were also no weather radars or seismic sensors capable of detecting such a complex geological event in the border region.
The FFD said it had already issued an early warning at 9:15 am on August 26, urging residents in the riverbank and other high-risk areas of Rasuwa, Nuwakot, Dhading, Gorkha and Chitwan to remain highly alert.
A total of 679,295 SMS alerts were sent through Nepal Telecom and Ncell, according to the division.
But while the number appeared impressive, the warning campaign proved ineffective in practice.
In the upper reaches, particularly Rasuwagadhi and Timure, the SMS warning reached people only a few minutes before the flood struck — far too little time to flee to safety.
Worse, dozens of Nepal Telecom and Ncell mobile towers and optical-fiber networks were swept away as the flood arrived, cutting off the communication network that could have carried warnings to downstream areas such as Nuwakot, Dhading and Chitwan.
The lack of backup systems such as satellite phones and VSAT made the situation even more critical.
In the very areas where timely information was most urgently needed, the infrastructure needed to deliver that information had already collapsed.
Seen in this light, the problem was not simply that warnings were not issued. The bigger failures were that they did not reach people early enough or for a sufficient period of time, while the infrastructure carrying those warnings was itself vulnerable.
The disaster made one thing clear: sending a large number of SMS messages alone does not constitute an adequate safety measure.
When ‘a big flood’ was not enough
Learning from the Bhotekoshi disaster, officials at the FFD have acknowledged the need for a fundamental change in the way warnings are communicated.
“The warning about the high-level flood like the Bhotekoshi was issued in the same way as a normal major flood. This is something we need to learn from,” a department official said.
According to him, the lack of clarity in the warnings increased the risk.
Even after being told that a major flood was coming, some locals went onto bridges to record videos, while even a police officer was swept away while using a microphone to warn people.
Based on this experience, he said future warnings should provide concrete and measurable information, such as how many meters above a certain level the flood is expected to rise, rather than simply announcing that a “big flood” is coming.
He said that although it was too late to save lives in Rasuwa because information about the flood was received only after it had arrived, timely warnings could have helped protect Bidur and Trishuli.
According to the official, it took nearly half an hour for the flood to reach Bidur from the area where it was first detected, providing enough time to save many lives.
“But we did not give clear enough information to make people flee immediately. People assumed it was like previous floods,” he said.
A local resident in Nuwakot echoed the concern, saying past experiences may have made people underestimate the warning this time.
“In the past, warnings were also issued about major floods, but only small floods actually came. So this time, too, people did not take the warning seriously and were caught off guard,” he said.
These experiences show that the weaknesses in Nepal’s early-warning system are not limited to technology or timing. The language, clarity and credibility of warnings are equally important.
The disaster demonstrated the danger of repeatedly issuing exaggerated or vague warnings: people may begin to normalize even genuine threats and fail to respond in time.
The risks beyond the warning system
According to flood analysts, Nepal also lacks an effective cross-border information-sharing mechanism. This has weakened the flow of critical information.
Even when information is available, there has been no clear contingency plan or regular drill to answer basic questions: Where should people in each area evacuate? How can workers inside tunnels be evacuated immediately?
The consequences were most severe in hydropower projects and settlements along the river.
“The river is flowing in its own place; the problem is with us,” an elderly local resident said, capturing the reality of the disaster.
Experts say the state has a responsibility to prevent the construction of major markets, hotels and customs infrastructure in highly vulnerable riverbeds and flood channels.
Hydropower projects such as Trishuli-3A and Chilime had not built protective walls or tunnel entrances capable of withstanding a flood and debris load of such unprecedented magnitude.
There are also concerns that environmental impact assessments were overlooked during the construction of the Galchhi-Rasuwagadhi road section and that indiscriminate mountain cutting weakened the terrain.
As a result, around 40 kilometers of road and dozens of bridges were swept away almost like houses of cards when the flood struck.
Ten days after the disaster, two workers were rescued alive from the Trishuli-3A Hydropower Project tunnel on Friday — a dramatic reminder of how terrifying the struggle inside the tunnel must have been. The full story of what happened inside remains to emerge.
Those involved in the rescue operation reportedly lacked not only modern equipment but even basic supplies such as boots suitable for working in mud.
Following the disaster, the government has begun installing CCTV cameras, seismometers and satellite internet in the Rasuwagadhi and Timure areas so that the situation can be monitored directly from Kathmandu. Experts, however, say these measures alone are not enough.
Their recommendations are broader: Nepal should make cross-border information sharing with China legally mandatory and automated; install seismic sensors and weather radars in Himalayan border areas; make Himalayan risk assessments mandatory when expanding hydropower projects, roads and settlements along river corridors; ensure future infrastructure is climate-resilient; and conduct regular evacuation drills at the local level.
The Bhotekoshi disaster has therefore raised questions that go far beyond the flood itself.
The challenge now is not simply to rebuild what the waters washed away. It is to learn why the warning failed to protect people, why critical infrastructure proved so vulnerable, and whether Nepal is prepared for the next disaster that may arrive without the warning signs it has traditionally relied on.
