A massive flash flood originating from Tibet caused widespread structural damage in northern Nepal. The deluge reportedly washed away villages and infrastructure project sites near the country's border.
The flash flood swelled the Bhote Koshi River at around 9 am local time before advancing downstream into the Trishuli River towards Nuwakot.
Most of the damage was located in northern Rasuwa, particularly in the Timure market area, the Timure Customs Office, and Syabrubesi. The district had a population of 50,000.
Hydrological experts say that the sudden deluge may have been caused by a Glacial Lake Outburst Flood (GLOF) in Tibet rather than localised rainfall.
The Bhote Koshi River originates in Tibet and empties into the Trishuli River before it flows into India as the Gandak River.
Nepal’s Department of Hydrology and Meteorology and administrative officers are collaborating with Chinese authorities to examine satellite data to pinpoint the origin of the flood.
Chinese researchers recently identified more than 130,000 rock glaciers on the Qinghai-Tibet Plateau. This number is more than the total number of rock glaciers identified worldwide previously, Ratopati reported. These rock glaciers contain 92 to 186 cubic kilometres of ice-equivalent water.
The water released from the glacial structure can affect river flow and the surrounding ecosystem in the long term. Changes in their movement can cause blockages or lead to a sudden increase in water volume.
Satellite imagery also showed heavy rainfall on the Tibetan side of the border.
Advisories have been issued for the riverbanks of Rasuwa, Nuwakot, Dhading, Gorkha, and Chitwan, with high water levels projected to reach the Marshyangdi confluence at Mugling by Wednesday evening.
Rasuwa district administrator Narendra Pariya told Reuters, "We have reports of villages and infrastructure project sites being washed away."
"There could be heavy casualties or loss of property," he added. "But I cannot say for sure now," he said.
Pariyar also said that it was not raining in the district headquarters area at the time of the flood.
Residents in low-lying riverside settlements and agricultural areas have been instructed to relocate to higher ground immediately.
Authorities have yet to release a confirmed toll of the deaths and damages. The full extent of damage in Syaphrubesi and Timure, among the worst-hit areas, is still unclear.
Nepal's water resources ministry said that hydroelectric projects were among the infrastructure damaged by the floods. Electricity supply in the areas has been disrupted due to the damage incurred. Production has been halted at facilities including the 111-MW Rasuwagadhi, Chilime, and Trishuli-3A hydropower projects.
Videos and photographs posted by residents from the affected areas show significant damage.
The Nepali Army, Armed Police Force and Nepal Police have been deployed for rescue and relief operations.
The exact cause of the flood and the full extent of the damage are being investigated.
