Nepalese officials said on Friday that the embankment of a barrier lake along the Nepal–China border in Rasuwa district has breached and water levels are rising. It comes hours after Chinese authorities warned that a failure could send a second surge downstream, the Indian Express reported.
China had earlier cautioned that Nepal could be hit by fresh floods if the lake embankment burst, and issued a Level-IV emergency alert over a newly formed barrier lake near the confluence of the Chhochen Khola and Purepu Tsangpo rivers. China’s Ministry of Water Resources put the lake’s volume at around 2 million cubic metres as of Thursday and said it was already overflowing, with another 3 million cubic metres expected to flow in over three days. The two rivers originate in Tibet and merge before crossing into Nepal, where the river is known as the Bhotekoshi — the principal upper tributary of the Trishuli.
The breach comes as the confirmed death toll from Wednesday’s flash floods stood at 469.
Nepal Police stated bodies have been recovered from eight districts. Chitwan has registered the highest toll at 178, followed by Nawalparasi East with 110, Gorkha with 44, Nuwakot with 37 and Dhading with 33. Another 28 bodies were found in Tanahu, 27 in Nawalparasi West and 12 in Rasuwa.
As per the latest update via PTI, 1,545 are injured and stranded people have been rescued, whereas 84 are undergoing treatment in Kathmandu. The operation involved 7,451 security personnel, including 2,392 Nepal Army personnel.
Wednesday’s calamity sent a torrent of water, mud and debris downstream through central Nepal, damaging houses, roads, vehicles and bridges and hydropower projects.
Nearly 1,000 missing: 133 Indians among missing
The search for those unaccounted for continues to go on. Around 1,000 people remain missing on both sides of the Nepal-Tibet border, including as many as 540 foreigners from 31 countries, as per Reuters.
Around 133 Indians were among those missing in the disaster. Flood alerts were also issued downstream in Bihar and Uttar Pradesh.
Survivor accounts underline the speed of the disaster. Janak Bahadur told Reuters that the flood “came in suddenly and exploded like a bomb”.
Another survivor, Diga Tamang, who was airlifted from hard-hit Rasuwa said, “All of our people have gone. They are dead.”
China races to contain fresh flood threat
The danger has not passed. Nepal and China have cautioned about fresh flooding, with debris dams creating two barrier lakes on either side of the border that threaten to collapse, Reuters reported.
China has deployed an eight-member engineering team to conduct aerial surveys and 3D modelling of one lake. It is around 150 metres long and 40-50 metres deep and holds an estimated 1.5 million to 2 million cubic metres of water.
Another 3 million cubic metres of water, roughly 12,00 Olympic swimming pools, could enter the lake over three days, creating a high risk of a breach. Perak flow is likely around September 1.
Rain around the Gyirong border port area has also loosened and destabilised surrounding soil and rocks, with more rain forecast over the coming week.
According to Reuters’ report, engineer Chen Hanxiao said, “After the glacier collapse created the lake, many isolated cliffs and steep cliffs appeared along it.” Engineers are planning to excavate a drainage channel through the debris dam to reduce the threat.
What triggered the deadly Nepal flood?
Scientists are surveying a glacier collapse and ice-rock avalanche as the prominent explanation. A large mass of ice and rock may have fallen into the Lhende River, temporarily blocking it and creating a landslide dam, before the blockage gave way.
“We suspect an avalanche on the Nepal side blocked the Lhende,” Kathmandu University professor Rijan Bhakta Kayastha told The Kathmandu Post, as quoted by PTI.
Earlier, the US Geological Survey termed the seismic event a magnitude 4.4 earthquake. It later concluded that the energy was generated by a glacial collapse and debris flow, not an earthquake and subsequently categorised the event as magnitude 5.2.
International Centre for Integrated Mountain Development (ICIMOD) data, as cited PTI, depicted the Trishuli River at Galchchi surging by as much as nine metres in just 30 minutes, whereas the level at Malekhu claimed around 7 metres.
As the Indian Express report mentioned, Nepal’s steep Himalayan terrain and narrow river gauges can accelerate floodwaters, while damaged roads and bridges make rescue operations more risky.