Scientists have pinpointed the collapse of a glacier as the cause behind the catastrophic flash flood on the Nepal-Tibet border, which has resulted in the loss of at least 177 lives. This tragic event has raised alarm bells about the increasingly rapid melting of ice in the Himalayas.
Initially, many suspected that an earthquake was responsible for the disaster. However, the US Geological Survey dispelled these assumptions by confirming that the flood was triggered by a "glacial collapse." This occurs when a glacier or a section of it breaks apart, and in this instance, the force was so powerful that it registered a 5.2 magnitude.
Dr. Simon Cook, a glacier specialist from the University of Dundee, noted that his research team identified the collapse of the lower section of a glacier near Langtang Lirung peak, situated roughly 15 kilometers west of where the flood hit. The collapsed glacier moved northwesterly before rushing downstream.
According to an analysis by the International Centre for Integrated Mountain Development (ICIMOD), an ice-rock avalanche from a high-altitude area might have triggered the calamity. This avalanche sent a tremendous amount of ice and rock debris into the Lende Khola, a tributary of the Bhote Koshi river, causing a sudden wave of water, sediment, and large boulders to surge downstream. Within half an hour, river levels skyrocketed by seven to nine meters, damaging several water monitoring stations.
Mike Searle, an earth sciences professor at Oxford University, explained that the sequence from landslide to flood could have taken hours or even days. He mentioned that the steep valleys in the region likely funneled the water at high speeds, worsening the flood's effects.
The exact reason for the glacier's collapse remains unclear. Searle suggested that the Langtang Lirung, like much of the Himalayas, is gradually rising due to tectonic movements, making the glacier steeper and more susceptible to collapse. Usually, smaller pieces break off and block rivers temporarily, but this time the entire glacier gave way "in one go, " something Searle described as "very unusual."
"These floods happen all the time, but not at this scale, " Searle commented. He believes the event was likely caused by a combination of tectonic activity and climate change, with rising temperatures accelerating glacier melt.
Experts have long cautioned about the melting ice and permafrost in the Himalayas due to climate change. An ICIMOD study earlier this year found that glaciers in the Hindu Kush Himalaya are losing ice at twice the rate since 2000, heightening flood risks.
Dr. Cook pointed out similar incidents of floods and landslides from glacier collapses in countries like India, Switzerland, and Italy in recent years. A major glacier collapse in Chamoli, northern India in 2021, led to a deadly flood that took 200 lives, with the impact compared to 15 atomic bombs.
Even in Nepal, the same region experienced flooding last year when a glacial lake in Tibet burst. Mohd Farooq Azam, an ICIMOD expert, remarked that the increasing frequency of such hazards in the cryosphere is becoming more evident. "The pace of change is so rapid, " he stated.
Though it is difficult to attribute any single event directly to climate change, Dr. Cook stressed that the pattern of these occurrences suggests a possible influence. "When you look at the pattern of these events, you do think climate change could have an impact, " he explained. "The logic is that with a warming planet, you will see shrinking glaciers, lots of snow melt. The permafrost that is partially holding some mountainsides together is warming and thawing and degrading." This leads to more landslides, debris flows, glacial meltwater, lake outbursts, and glacier collapses, as climate warming destabilizes high mountain regions.
