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Scientists have identified unusual signals recorded during the period of the disaster, and are now examining whether some signals are connected to the suspected avalanche.
Visuals of flash flood that hit northern Nepal. (Source: X)
A large volume of ice and rock debris may have entered the Lende Khola, a tributary of the Bhote Koshi River that could have generated a sudden surge that carried water, sediment and large boulders downstream, say experts as they begin investigations into the triggers behind the massive flash floods in north Nepal.
The preliminary assessment is based on video footage and information from affected areas, even as researchers wait to analyse more evidence emerging from the deadly disaster.
The sudden deluge in the Bhoti Koshi river has wiped off hundreds of villages downstream, as the death toll continues to mount. The flash flood struck Nepal’s Rasuwa district on Wednesday morning, sending a powerful surge of water, sediment and boulders through the Bhote Koshi and Trishuli river systems, raising concerns over further potential downstream impacts.
Scientists from Nepal-based International Centre for Integrated Mountain Development (ICIMOD), alongwith partner institutions in Nepal and China are investigating whether the flood may have been triggered by an ice-rock avalanche originating from a high-altitude area.
Hydrological observations analysed by experts at ICIMOD show the exceptional speed and magnitude of the flood wave. Water levels on the Trishuli River at Galchchi reportedly rose by as much as nine metres within 30 minutes, while levels at Malekhu increased by seven metres over a similar period.
Several water monitoring stations along the Trishuli River were reportedly damaged or washed away during the event, although the Glachchi monitoring station remains operational.
ANY SEISMIC ACTIVITY?
Scientists are also analysing the seismic records and the preliminary analysis, which identified unusual signals recorded during the period of the disaster. They are now examining whether some signals are connected to the suspected avalanche.
Data from a seismometer in Jilong, approximately 12 kilometres from the affected area showed anomalous signals, while a second station in Zhangmu also recorded unusual activity. However, they highlight that no causal link has been established between seismic activity and the flood till now.
“An ice avalanche in the Lhende Khola is the suspected trigger, but the cause remains unconfirmed,” said Qianggong Zhang, Head of Climate and Environmental Risks at ICIMOD.
DISASTER NOT OVER YET
Experts are also assessing whether debris temporarily blocked the river at a narrow section, forming a landslide dam. Such blockage can create a secondary hazard if impounded water is suddenly released. Authorities and scientists are continuing to evaluate the size, location and stability of any potential blockage.
But with a blockage still lodged upstream on the Nepal-China border, authorities warn a second flood is imminent and evacuation orders are now in place for Jilong port.
According to local reports, water levels in the Bhote Koshi basin began rising rapidly around 9:00 AM local time on August 26. The flood breached riverbanks and travelled downstream through the Bhote Koshi River into the Trishuli River, with potential impacts extending into Nuwakot and Dhading districts.
MASSIVE DESTRUCTION AS DEATH TOLL RISES
The flood has caused significant damage to infrastructure in the affected areas, including hydrological monitoring stations. Several hydropower facilities are located along the Bhote Koshi River and connected river systems.
“We are deeply saddened by this tragic disaster, which struck so suddenly and unexpectedly,” said Pema Gyamtsho, Director General, ICIMOD, adding that the exact cause is yet to be ascertained.
Experts also drew attention to the extreme vulnerability of the Hindu Kush region which stretches 3,500km across Asia, spanning eight countries. “The increasing frequency of cryosphere hazards is becoming more visible than ever before. The pace of change is so rapid that current efforts are struggling to keep up,” said Mohd. Farooq Azam, Senior Cryosphere Specialist at ICIMOD.
Experts are analysing hydrological, seismic, remote-sensing and field data to better understand what triggered the event and assess ongoing risks to downstream communities.
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Ask News18Scientists are examining whether unusual seismic signals recorded during the disaster are connected to the suspected ice avalanche.
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Srishti Choudhary, Senior Assistant Editor at CNN-News18 specializes in science, environment, and climate change reporting. With over a decade of extensive field experience, she has brought incisive g…Read More
August 26, 2026, 11:11 PM IST
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