21 August, Kathmandu. Two weeks ago, 1,300 people died in the flood of Rasuwagadhi, while nearly 5,000 people are still missing. The flood which damaged from Rasuwa's Timure Naka to Nuwakot's headquarter Vidur and Devighat Bazar badly damaged about half a dozen hydropower projects. The number of people estimated to be trapped in the tunnels of the hydroelectric project is about 900.
Not only in Nepal, but also in other countries with high mountains and Himalayas, there are not many examples of this level of destructive disaster. Some experts say that although there is no damage and loss of this level, the incident that happened five years ago in Chamoli, India, is of the same nature and similar.
On February 7, 2021 (25th of March, 2077), a sudden and devastating flood occurred due to the fall of huge snow and rocks in the lap of Nanda Devi Himal in India. The incident in Chamoli district is known as 'Chamoli flood' among experts.
The flood which has lost around 300 people and damaged four hydroelectric projects is not as terrible and destructive as Rasuvagadi, but the cause of the incident, the after effects and some of the symptoms seem to be similar.
"Five/six months before the Melamchi flood in Sindhupalchok, there was a flood in India's Chamoli, which is similar to the Rasuva flood," says Santosh Nepal, a water resources expert, "Glacier and ice-rock fell down from the Nanda Devi mountain range. It took Hiu and the other Gegrans with them. The snow that had flowed immediately melted and there was a large-scale flood, causing great loss of life.
Be it Chamoli or Rasuwagadhi flood. Immediately after the incident, experts speculated that the flood might have been caused by the explosion of a glacier. But after satellite data became available, their estimate changed within a few hours.
The Nanda Devi incident occurred after the Himtal blast - glacier lake outburst flood - (glof) but rock and glacier mounds fell down. The fall of the rocks in the high Himalayan area and the accompanying mounds of snow are considered to be the cause of Chamoli and Rasuva floods.
A snow mound with rocks fell from a height of about 5500 meters from a place near Ronti peak in Nandadevi National Park. The friction generated by the rapid descent of the snow and rock was converted into energy and the snow immediately melted and became a flood.
Five years ago, the place where the rock and snow fell is near Nanda Devi (7816 meters), the second highest mountain in India. The mound fell straight down from the high mountain range with steep terrain.
The flood started when the Rishiganga river, which joins the Raikhana glacier, was blocked, which later joined the Dhauliganga and caused further destruction. The flood at 10:30 in the morning was as destructive and rapid as Rasuvagadi.
Although it was thought that a glacier had exploded immediately after the incident, after about 7/8 hours, by analyzing the satellite data, the experts discovered the remains of the landslide under the Ronti mountain near the peak of Nanda Devi.
According to the ISIMOD study report, the rocks and landslides blocked the Rishiganga river for some time, causing severe flooding in the low-lying coastal areas after the temporary dam burst.
In the last week's incident, when the rocks and mud mounds in the northern part of Langtang-Lerung fell, was the Lhende river blocked or not? If it was stopped, it is not clear how long the water stopped.
Landslides are bigger, but the nature is the same
In the Nanda Devi incident, there was extensive damage to the watersheds of Rishiganga, Alkanand and Dhauliganga rivers that flow from there. The devastating flood that came down at a very fast pace like in Nepal caused great damage to the Tapovan Vishnugad Hydroelectric Project and the Rishiganga Hydroelectric Project.
Snow expert Dr. According to Arunbhakt Shrestha, the loss of Rasuwagadhi is much greater than the Chamoli flood which caused a 'human loss' of around 300 people who were lost and died.
"There were no settlements around the flooded area, there were many people related to the hydroelectric project," says Shrestha, "dozens of settlements were washed away in our area, and it has affected far down. In terms of human and structural damage, there is a huge loss. In Nepal, only about 900 people working in hydropower projects have been lost.
Eight years before Nanda Devi's glacial landslide and Chamoli flood, there was a major flood in the Kedarnath Valley in Uttarakhand, India. The Chamoli incident took place about 60 km northeast of the Kedarnath flood-affected area.
The reason and nature of the flood of Nanda Devi and Rasuwagadhi here is not the same as the Kedarnath flood in which nearly 6,000 people died or went missing. The Kedarnath flood that affected Rudraprayag, Chamoli, Uttarkashi and Pithoragarh districts was caused by very heavy rains (cloud bursts) for a few days, not landslides in the Himalayan region.
After the study of the Nanda Devi landslide, it was discovered that the rocks had separated before the incident and that the cracks had started to form some time ago at the place where the landslide occurred. Some experts have made a preliminary conclusion that before the Rasuwagadhi flood, before the landslide on the northern side of the Langtang-Lirung mountain, the glacier was moving abnormally and small tremors were generated a few hours ago.
According to the study at that time, it was found that 85 percent of the rock and 15 percent of the ice in the flood that occurred after the landslide in the Nanda Devi Himalaya. The experts concluded that the immense energy generated after the iceberg falls would be enough to melt a large amount of snow immediately. After that, they estimate that the water flowed rapidly after the ice melted.
Some experts have expressed 'surprise' that there was a severe flood compared to the proportion of rocks and mudslides that fell in the Rasuwagadhi flood, while some have made a preliminary analysis that the size of the flood on the lower side of the rocks, rocks and Gegran Misida was larger.
Dr. who has studied in the Himalayan region for a long time. Arunbhakt Shrestha says that the landslide in the northern part of Langtang-Lirung is much bigger than the landslide in Nanda Devi. According to him, in Nanda Devi, the peak of Ronti peak fell, while in Rasuwa, the rock and part of the glacier above it fell down.
Shrestha, a senior climate expert at ISIMOD, says that the nature of the Seti flood in Pokhara 14 years ago, the Nanda Devi landslide and the Rasuwa flood are similar. Seti, which was trapped after the fall of a pakha next to Annapurna 4th Himal, later took the shape of a flood.
Comparing the nature of the landslide, climate expert Shrestha says that the Ronti peak of Nanda Devi and Annapurna 4th are similar. He says, "In comparison to Seti and Chamoli, a part of the glacier and the rock beneath fell in the landslide of Langtang, which is considered to be the cause of the Rasuva flood."
According to a study conducted by a team including Arunbhakt Shrestha, Santosh Nepal, Ghulam Rasul and Birendra Bajracharya in Chamoli, three days before the incident, i.e. from 4 to 6 February, it rained in the area around Nandadevi Himal due to the influence of western winds.
Analyzing the record of 58 mm of rain in a period of three days (72 hours), the researchers have estimated that Nanda Devi and Ronti Peak area located near it may have been snowfall instead of rain.
They did not consider rain to be the main reason for the rock and hail fall, rather they estimated that it could also be a reason. There was no flood here in the Langtang area, there was only 8.8 millimeters of rain in a period of 72 hours.
Nanda Devi's landslide happened not during summer like in Rasuwagadi, but when there was severe weather. According to various studies after the Nanda Devi landslide, parts of Uttarakhand in India had their "hottest January" on record for six decades. During the study, there was a dramatic reduction in snow cover.
Recently, the temperature in Langtang area is higher than normal. In the summer of 2026, the temperature was minus 38 degrees Celsius higher than the average temperature, while in the summer of 2026 it reached minus 58 degrees Celsius. In both the landslide incidents, the temperature range is also seen to be similar.
The researchers concluded that Chamoli floods cannot be linked as a direct effect of climate change. However, he estimated that the cycle of increasing melting and freezing of the ground and ice connecting parts (permafrost) of the Himalayan region may have partially contributed. The melting and freezing of permafrost is considered by some to be an effect of climate change. The researchers have analyzed that the Chamoli flood may have occurred due to a combination of various events and reasons.
The flood that started after the Nanda Devi landslide broke the 60 meter diversion dam of the Rishiganga hydropower project, which caused the flood to spread even further when the water stored there also flowed. The flood damaged four hydropower projects and damaged other structures about 125 kilometers downstream.
The flood of Rasuwagadhi has badly damaged more than half a dozen hydropower projects. But a large amount of stones and rocks flowed from above and piled up in the dam. After flowing down from Bhotekoshi, other tributaries did not become a factor in increasing the flood.
Foreshadowing: Was it or wasn't it?
According to the study team's estimate, a huge pile of rock, ice and snow of about two and a half million cubic meters had fallen there. Compared to that, the rocks and snow mounds that fell from the Langtang-Lirung area are very large.
Some experts have estimated that at least two and a half million cubic meters of the import pile has fallen from the upper level, while others have said that the base of import may be 100 million to 200 million cubic meters. Which is much bigger than the landslide of Nanda Devi five years ago.
In a research article published in 'Communications Earth and Environment', the amount of snow that melts in the Himalayan region is more than the amount of snow that accumulates throughout the year, which is a major indicator of the melting of glaciers. Apart from that, due to the increasing rainfall in the Himalayan region, the warming of the Himalayan land, landslides including rocks and icebergs are increasing.
In their study, the scientists have analyzed that some seismic signals were seen before the avalanche with rocks on the slopes of Nanda Devi. Two and a half hours before the incident, there was a general tremor of the ground shaking.
According to the data of the preliminary study, the opinion of scientists has been made public that there were seismic signals even hours before the landslide in the northern part of Langtang-Lirung. Nanda Devi and Langtang-Lirung region's initial and indicative signs before the landslides are also similar.
After the Chamoli incident, scientists analyzed satellite data around Nanda Devi. During that time, the Ronti peak with Nanda Devi had developed cracks, the structure of the ice surface had started to change and the signs of temperature change were observed.
Those studies have concluded that changes in the slope of the land were visible even before the incident. But their analysis is that those symptoms were not recognized as premonitions before the incident.
Outbreaks other than 'Gloof'
Both the Chamoli disaster and the Rasuwagadhi flood destroyed the structures in the low-lying areas, so it can be termed as a 'structural disaster'. Even though the experts have analyzed the incidents of Rasuwagadhi rock and Hiu hill falling under the technical names like 'Glacier Collapse', 'Ice-Rock Avalanche', 'Landslide-Cascade', they have not published a detailed study summary.
In the past, scientists used to consider flash floods (called flash floods) to be a form of post-rainfall floods. Even without heavy rains or avalanches, such floods have started to increase.
Scientists have also started calling such events 'blue sky floods'. He said that the situation where the sky is blue means that there is not much rain, even when the weather is clear, there are other reasons for the increase in floods.
The Chamoli flood affected the area from the point of origin to about 60 km downstream, while the Rasuwagadhi flood has damaged structures from Rasuwagadhi to Galchi, which is about 200 km. Compared to Chamoli, not only the flood of Rasuwagadhi, its size, loss of life and the affected area is also very large and wide.
The Chamoli and Rasuwagadhi floods have established the fact that 'Devastating floods can occur even if there is no rain in the Himalayan region and the snowmelt does not explode.'
In both Rasuwa and Chamoli, the flood speed in the upper reaches was abnormal and very rapid. The import of the flood that reached the valley was much greater than that of the falling rocks and hail. It is known from the videos available on social media that the nature of both floods is similar in the activities of building roads and bridges and destroying structures.
It is not clear whether climate change is the main cause of Chamoli incident. In Nepal, a study has been started about floods. But according to analysts, the reason for both the incidents is the rising temperature in the Himalayan region.
"New thinking in early warning"
According to experts, there have been many floods in Nepal due to falling icebergs and glaciers. Seti, Thame, Bhotekoshi and other floods are examples of that. However, compared to him, there is more concern about Himtal and its explosion.
Climate expert Arunbhakta Shrestha admits that there is a lot of talk and discussion about Himtal explosions and subsequent floods (glofs) and their risks, and in recent years other avalanche disasters besides Himtal explosions are on the rise. According to him, compared to others, monitoring and forecasting events such as avalanches and glaciers are relatively complicated.
"After an incident occurs in a place, it becomes easy to collect data and analyze it, but before the incident, how do we know that the incident is happening in that place?," says Shrestha, "Therefore, the task of estimating the incident of falling icebergs, avalanches and glaciers is a bit complicated."
Birendra Bajracharya, a senior geoinformation expert (Senior Geoinformation Specialist) involved in the Nanda Devi landslide study team, believes that the traditional approach to disaster in the Himalayan region will change after the Chamoli and Rasuwa incidents.
According to Bajracharya, as easy as it was to prepare for a disaster by looking at the size of a glacier or measuring the surface of a river, now it has become imperative to develop more advanced and effective mechanisms to avoid sudden disasters. It is not impossible to monitor by placing a radar in a place where there is a possibility of avalanche, but it is very difficult to predict the place where the avalanche will go.
"Yesterday, it was easy to see the size of the glaciers and make risk-wise preparations, but now it is more difficult to see the risk of landslides in the high Himalayan region," says Bajracharya, "The Rasuwa incident has taught a lesson that research in the Himalayan region needs to be transformed. Now we have to think about the method of forecasting accordingly.
Gyawali, who writes on judicial and government matters, compiles investigative content in online news.
