The catastrophe began in the Lhende Khola river, a tributary of the Bhote Koshi located in a steep area of the Himalayas. The preliminary explanation points to a landslide of ice and rocks falling onto the riverbed, forming a natural dam and causing a huge accumulation of water.
When the blockage gave way, the water rushed down the valley mixed with mud, stones, and remnants of vegetation. The current reached towns, border posts, and hydroelectric works with hardly any margin to evacuate the population.
What has happened in Nepal
The flood reached around 9:00 local time the district of Rasuwa, north of Kathmandu. The water first hit the vicinity of the border and then advanced along the Bhote Koshi until it joined the Trishuli river. The current has severely destroyed settlements such as Timure, Rasuwagadhi, and Syabrubesi. Images broadcast from the area show collapsed buildings, vehicles buried in mud, and bridges torn from their bases.
The damage has also extended to the Tibetan side. The mudslide reached the land port of Gyirong and cut off roads, communications, and electricity supply in this border area of China.
The Nepalese police have reported at least 95 bodies recovered, although the toll remains open. The Ministry of Tourism estimates that 341 foreign travelers are still unaccounted for, while dozens of Nepalese citizens are also missing. Among them, at least two Spanish citizens were among the missing persons, although their identities are still unknown.
Many of the travelers were heading to Mount Kailash and Lake Mansarovar, sacred places for Hindus, Buddhists, and Jains.
How the flood occurred
A sudden flood of this type can begin without it raining heavily in the place where the rise appears. The water comes from an area upstream and reaches the valley suddenly. The hypothesis put forward by the Nepalese authorities describes the following sequence:
- A mass of ice, snow, and rocks detached in a high mountain area.
- The material fell onto the Lhende Khola river and temporarily obstructed its course.
- The water continued to accumulate behind the blockage until it formed a natural dam.
- The pressure eventually broke or overflowed that barrier.
- The accumulated water descended down the valley accompanied by mud, rocks, and debris.
This phenomenon explains the appearance of a wall of water and sediments capable of dragging buildings, vehicles, and bridges. It was not just a progressive increase in the river level, but rather a sudden and concentrated discharge of water coming from the mountain.
The satellite images analyzed by the National Authority for Disaster Risk Reduction and Management of Nepal show an ice and rock avalanche approximately 20 kilometers northeast of the Rasuwagadhi border crossing. The material would have fallen onto the Lhende Khola before the flood advanced towards the Bhote Koshi.
The earthquake that possibly triggered the avalanche
The German Research Center for Geosciences recorded a magnitude 4.4 earthquake near the border with Tibet a few minutes before the cameras began to record the flood. Nepal's Foreign Minister, Shishir Khanal, has suggested that the earthquake may have caused the landslide that blocked the river. The temporal coincidence supports that possibility, but it does not yet demonstrate a direct relationship.
Researchers must determine whether the earthquake destabilized the slope, whether the mass of ice and rocks was already about to detach, or whether other factors were involved. The connection between the earthquake and the avalanche remains a hypothesis, not a definitive conclusion.