What triggered Nepal's deadly floods? Experts point to Tibetan glacial lake drainage as rescue ops intensify

Officials said that among the nine confirmed fatalities, eight bodies have been brought to Kathmandu for autopsy, with one already identified and handed over to the family.

A devastating flood in Nepal’s Bhote Koshi River, which claimed at least nine lives and left more than 25 people missing, was likely caused by the sudden drainage of a supraglacial lake in Tibet, experts revealed on Wednesday. The lake, located north of Nepal’s Langtang Himal range in China’s Tibet Autonomous Region, emptied rapidly, triggering a flash flood that wreaked havoc in the Rasuwa district near the Nepal-China border.

The International Centre for Integrated Mountain Development (ICIMOD), based in Kathmandu, confirmed through satellite imagery that the flood was linked to the lake’s drainage. Sudan Maharjan, a remote sensing specialist at ICIMOD, said their preliminary analysis indicates a supraglacial lake burst as the origin. These lakes form on glacier surfaces and grow from accumulated meltwater, sometimes becoming large enough to pose flood risks.

The torrent not only destroyed local infrastructure but also washed away the Friendship Bridge, a symbolic and functional link between Nepal and China. It severely damaged the Rasuwagadhi Hydropower Plant and the Inland Container Depot supported by China, located near the border. Six Chinese nationals working at the facility remain among the missing.

China’s state media reported that 11 individuals were unaccounted for on the Chinese side, while in Nepal, authorities are still searching for 19 people, including two police personnel. The early-morning flood on Tuesday struck without the usual monsoon warning signs, leading officials to suspect it wasn’t solely driven by rainfall.

Dinesh Bhatta, Director General of Nepal’s National Disaster Risk Reduction and Management Authority (NDRRMA), said the water level surged to 3.5 metres despite no heavy rain on either side of the border — an anomaly that supports the glacial outburst theory. “We are working with experts to investigate the actual cause,” Bhatta added.

Meanwhile, rescue and relief operations intensified. Arjun Paudel, chief district officer of Rasuwa, said over 150 people — including 127 foreign nationals — were evacuated and airlifted to Kathmandu. Communication and electricity services were disrupted in the region, but efforts are ongoing to restore connectivity through the Chinese border.

Officials said that among the nine confirmed fatalities, eight bodies have been brought to Kathmandu for autopsy, with one already identified and handed over to the family.

According to ICIMOD’s Saswata Sanyal, such glacial lake-related disasters are increasing at an “unprecedented” rate across the Hindu Kush-Himalayan region, which spans eight countries. He emphasized the urgent need to study these cascading events more deeply as climate change continues to accelerate glacial melt and extreme weather patterns in the region.

The monsoon, which typically lasts from June to September, routinely brings landslides and flash floods to Nepal’s mountainous terrain. However, this year’s rainfall, which started early, has already caused significant damage, with at least 38 people killed or missing nationwide since May 29.