© UN-Nepal/A. Das The Himalayan mountain range extends throughout Nepal. As the Himalayas melt: fatal floods become the norm Fabrice Robinet Climate and Environment
Just a day before a giant wall of ice, rock and mud descended on the Himalayan valleys near the Nepal-China border, climate scientist Dipesh Chapagain was discussing with a colleague the scale of the catastrophe that such a disaster could cause.
For the 40-year-old researcher, who grew up in the hills of eastern Nepal and now works at a branch of the United Nations University in Bonn, the topic is not only professional, but also deeply personal. Changes that threaten the region are happening right before his eyes.
“When I was a kid, things were different,” he shares. “Neither my parents nor my grandparents faced such threats on such a scale.”
Disasters are occurring more frequently
On Wednesday at 8:37 a.m. local time, part of a mountain range collapsed in the Himalayas. The rocky base under the glacier could not stand it, and a colossal mass of ice and rock fell down, covering about 1200 meters vertically. The rivers poured out a torrent of water, sediments and boulders. It washed away several settlements along one of the most important trade routes linking Nepal and China. At one of the hydrological posts, the water level rose by nine meters in just half an hour.
© UN/O University. Gonzalez Dipesh Chapagain at the United Nations University in Bonn, Germany.
By Friday, the death toll in Nepal and Tibet had exceeded 500 people, with more than 1.5 thousand still missing, including hundreds of foreign tourists.
Chapagain’s family was not injured, but the news resonated with pain in him.
“Every time It’s unbearably difficult to receive such news from home,” he says. “And these disasters are happening more often and becoming more destructive.”
What happened is a harsh confirmation of the fears of climatologists. The ice framework of the Himalayas is rapidly changing, and millions of people find themselves defenseless against elements whose behavior is becoming increasingly difficult to predict.
How a mountain collapse turned into a deadly torrent
Scientists continue to reconstruct the chronology of Wednesday’s events. Analysis of satellite images shows that the bedrock beneath the glacier has lost stability, causing a mass of ice and rocks to flow into the Lhende Kholu, a tributary of the Bhote Kosi River. This set off a cascade of destruction.
The mechanics of the disaster are different from the glacial lake outbursts that Dr. Chapagain studies as part of the Mountain Research Program at the United Nations University Institute for Environment and Human Security. Chapagain and his colleagues focus on the Hindu Kush Himalaya region.
According to program data covering the period from the beginning of observations to 2024 (a total of 493 cases), the frequency of lake outbursts has increased approximately fivefold since 1950, from seven to 34 cases per decade.
Typically, these floods occur when meltwater accumulates in reservoirs near retreating glaciers, often held by unstable ice or loose rocks and sediments. When such a natural dam breaks, a huge volume of water is released almost instantly.
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However, on Wednesday the scenario was different. “There was no intermediate stage this time,” Chapagain explains.
Instead of a gradual accumulation of water in the lake, a sudden collapse of rock and ice occurred. Researchers are now testing the hypothesis that the debris could block the river for a short time, forming a temporary dam, which then collapsed under the pressure of water (this version has not yet been officially confirmed). settlements.
It is too early to say whether it was the climatic factor that caused the collapse. However, global warming is rapidly changing the high-mountain environment: melting glaciers and degradation of permafrost deprive rock masses of stability, and meltwater erodes the slope, reducing its strength.
The consequences extend far beyond the high mountain villages. The Hindu Kush-Himalaya massif feeds 10 of Asia’s largest river basins, on whose resources 2.1 billion people depend.
At risk
It’s not just the mountain landscape that is changing – the geography of people’s settlement is also changing.
Dipesh Chapagain recalls what happened in his childhood Residential houses in the mountainous regions of Nepal were traditionally built higher on the slopes, and the lowlands near the rivers were used for rice crops. His family’s home was on top of a hill, and the rice-growing plots were below, near the water.
Over time, infrastructure – roads, factories, hotels and hydroelectric power stations – began to concentrate in river valleys, where it was easier to build and do business. In addition, drinking water sources located at high altitudes are gradually drying up, forcing people to descend lower.
This has led to a dangerous trend: As warming weather erodes mountains, populations and key infrastructure are concentrated directly in the path of potential mudflows and water flows.
© UNICEF/L. Prasad-Ngahusi Buildings and streets in communities in Nepal’s Bagmati province are covered in mud.
The valley damaged on Wednesday is a clear example of such development. Along the Bhote Kosi – Trishuli transport corridor leading to Kathmandu, there are hydroelectric power stations, bridges, hotels and residential areas. The flood destroyed energy facilities and disrupted transport and information communications throughout the region.
The potential danger was obvious, disasters had occurred before: just a year ago, a burst of a glacial lake in the same river system claimed the lives of nine people, and another 24 were missing. alerts.
Nepal authorities learned about the approaching flood only when the flow was already approaching the border. Alarm signals were transmitted via SMS, social networks, calls and emergency alerts on phones.
According to Chapagain, the risk of floods can only be reduced by taking a set of measures at the earliest stages: constant monitoring of glaciers and unstable slopes using satellites, expansion of the network of meteorological and hydrological posts, as well as the introduction of early warning systems that give people time to evacuation.
Given the transboundary nature of rivers and glaciers, China, Nepal and downstream countries must establish rapid data exchange.
But there is a deeper problem. Even if greenhouse gas emissions drop sharply, glaciers will continue to lose mass for several decades due to the inertia of the climate system. Humanity can still influence how much ice will remain in the long term, but scientists are not able to prevent the processes that will occur in the coming years.
This means that adaptation to new conditions is not preparation for the distant future. For the inhabitants of the Himalayas, this future arrived on Wednesday.