How the deadly Nepal and Tibet flash flood unfolded – a visual guide
US Geological Survey says massive glacial collapse caused catastrophic flash floods in the Himalayan border region of Nepal and Tibet
At 8.37am on Wednesday, an enormous section of a glacier in the Himalayas sheared free and crashed on to the valley floor in Nepal’s Langtang national park, about 35 miles (60km) north of the capital, Kathmandu, near the mountainous Nepal-Tibet border.
Such was the force of the event, it was initially reported as an earthquake of magnitude 4.4. The US Geological Survey later determined the tremor was caused by glacial rock and ice collapsing, registering a magnitude of 5.2.
The collapse triggered a huge release of water, mud, rock and ice that thundered down valleys and swept down the Lhende, Bhotekoshi and Trishuli rivers.
The high-speed flash floods careered towards northern Nepalese towns, including areas popular with mountaineering tourists and pilgrims.
Horrifying videos from the Gyirong border post, which connects Nepal and Tibet, showed people running for their lives as the wall of debris obliterated buildings and swept away lines of buses.
In Nepal, houses and roads were washed away in seconds. “It was a huge gush of mud coming straight towards us,” said Keshav Prasad Baral, a 68-year-old survivor who was being treated at a small hospital. “As it got closer, it kept rising higher and higher. When I saw it enter our home, I tried to grab my wife’s hand and take her to the terrace. But she was swept away by the mud. Four or five hours later, a helicopter came to rescue me. My wife is still somewhere beneath the mud. She’s gone.”
Another survivor described being saved by clinging to a mango tree as he watched the house where he had been working disappear.
In a stark illustration of the deluge’s deadly power, a bridge crossing the Trishuli River was shown in a video being washed away in a tsunami-like flood. Multi-level homes were quickly submerged as the torrent gouged through the riverside town.
Bibek Kumal, a Nepali labourer, had been working in Bidur when others sounded the alarm. “I started running. Then a wall of water came thundering down as if it was an earthquake,” Kumal said from his bed at Kathmandu’s National Trauma Centre.
The torrent had swept him downstream amid mud and debris but “luckily I was stuck up in a mango tree”, he said. “Had there been no mango tree, I would have been washed away to death.”
At a location just north of Kumal’s lucky escape in Bidur, a video shows an immense flood swallowing a river valley as it surges towards Betrawati Bazaar, an important historical and pilgrimage town.
Mud and water moving at such high speeds forms a lethal combination “like liquid concrete” that cannot be outrun, said Hatim Sharif, a hydrologist at the University of Texas San Antonio. Satellite imagery taken above Kolpurtar shows how the mud, water and debris swallowed up land on either side of the river.
Rescue operations were difficult on Wednesday because of damage to infrastructure and higher than normal river levels. Helicopters could not land in Nepal’s affected areas of Syapru Besi and Timure, in the Rasuwa region, which has a population of about 50,000.
Rescuers waded through mud and sludge looking for survivors after flood waters buried the lower floors of multi-storey buildings.
“There is devastation everywhere we look,” Tula Bahadur BK, a health worker in Rasuwa, told Reuters. “The settlements next to the river have been completely swept away. Five of my own relatives are missing.”
Dave Petley, an earth scientist with Nottingham Trent University, described the scale of the event as close to “apocalyptic”. The huge volume of water was possibly a combination of ice that converted to water as a result of the initial collapse and river water. But until the exact cause of the disaster could be confirmed by scientists, that was just speculation, he noted in the science outlet Eos.
The Himalayan mountain range spans several countries in south Asia and has many of the world’s highest peaks and remaining glaciers.
The steep slopes and the lush valleys below are especially vulnerable to flooding and landslides, and extreme weather events such as intense monsoons and melting glaciers have become more common because of warming due to human-caused climate change.
Researchers in Kathmandu found earlier this year that glaciers across the Hindu Kush Himalaya region were melting faster, with ice loss rates doubling since 2000.
With Reuters and Associated Press