Kathmandu. International experts have investigated the devastating Bhotkoshi floods of August 10. They have found out the initial cause of the flash floods. However, they are still in the investigation.
According to a new scientific analysis by more than 20 international experts, the devastating floods on the Nepal-China border are the result of a combination of complex factors. Many of these have been exacerbated by human-induced climate change.
The region is still reeling from the effects of a devastating iceberg avalanche that flows through narrow mountain valleys. It destroyed cities, roads and bridges. At least 1,300 people have died and more than 5,000 have gone missing.
As rescue efforts turn into recovery efforts and the country embarks on a massive reconstruction effort, scientists around the world are trying to understand what caused the tragedy.
According to experts, on August 20, a huge chunk of rock and glacial ice, about 2,000 feet wide, burst from the Langtang Lirung mountain and fell into the river about 7,000 feet below. This released energy equivalent to a 5.2 magnitude earthquake. It fell so fast that the ice melted almost immediately. The flow also carried wet soil and debris and probably collided with the snow buried in the valley floor. As a result, the flood wave became more powerful and traveled more than 20 miles.
Walter Immergil, a mountain hydrologist at Utrecht University in the Netherlands, described it as an “unprecedented disaster” in the Himalayas.
A team of glaciologists and climate scientists from World Weather Attribution (WWA), a network that investigates the role of climate change in extreme weather events, released its preliminary analysis report on Wednesday. According to the report, the disaster was not caused by a single extreme weather event. It was caused by the interaction of many processes. It has caused global warming due to fossil fuel pollution for decades.
Scientists found that a 7.8-magnitude earthquake in 2015 may have caused an avalanche of rock and ice to fall from the southern part of the mountain, weakening the slope and causing the mountain to collapse. “Since then, the number of landslides in the mountains has increased,” the report said.
The scientists then looked at the role of climate change and found that many processes were operating simultaneously. Climate change is pushing the ‘zero degree’ line in the Himalayas. The point in the atmosphere where the temperature reaches 0 degrees Celsius (32 Fahrenheit) and exceeds 320 feet every decade.
The report notes that rising temperatures are weakening permafrost (a mixture of snow, rock, sand and soil, a mixture of snow, rock, sand and soil, especially in the high mountains of Nepal near the height of the event. Which can act as glue). “Permafrost melting reduces the strength of the rock and allows more water to flow down the slopes,” Imrazil said. ’
Glacier changes are another important factor. The report notes that the Langtang-Lirung glacier has thinned and contracted significantly in recent decades, especially after 2010. As a result, the slope has become less stable and meltwater has seeped into the rock cracks.
The researchers also looked at the weather conditions before the event. Last fall, October and early November, the region received heavy snowfall. Then July and August were the hottest months on record locally. That generated large amounts of meltwater and further weakened the slopes.
Using historical data and climate models, the researchers found that July and August temperatures in the region are now about 1.5 degrees Celsius (2.7 Fahrenheit) higher due to climate change. The annual temperature in the region has increased by 2 degrees Celsius (3.6 Fahrenheit). This is significantly higher than the global average.
The study found no clear link between global warming and increased snowfall and rainfall. However, Frederick Otto, a professor of climate science at Imperial College London, said, “There is no doubt that human-induced climate change played a role in creating the preconditions for this disaster.” ’
The scientists concluded that the event was unlike anything previously experienced in the region in terms of its size, speed and complexity. “None of the existing early warning systems could provide enough time,” they said.
“This is one of those events that is beyond the limits of our adaptability,” Otto said. “Unless the world rapidly reduces fossil fuel pollution, we will definitely see many more disasters of this level.” —from CNN
