A day after a massive flood in the Bhotekoshi River caused widespread destruction in Rasuwa and affected downstream areas of Nuwakot, Dhading and Gorkha, questions remain over what triggered the disaster.
While some Nepali experts have raised the possibility of a glacial lake outburst flood (GLOF) or a combination of cascading events in Tibet, the Chinese side has attributed the disaster to an earthquake on the Nepali side that allegedly triggered an ice avalanche and subsequent mudslides.
Foreign Minister Shishir Khanal, speaking in Parliament on Wednesday, said that initial information has been received about an earthquake in Tibet and that it may be related to the flooding in the Bhotekoshi.
Climate change expert Ujjwal Upadhyaya said the nature and scale of the flood suggested that a GLOF could be one possible explanation, although he stressed that this was only an initial assessment. “Looking at the nature of the flood, it appears like a glacial lake outburst flood,” Upadhyaya said, adding that rising global temperatures and increased atmospheric temperatures in the region could be increasing the risk of such events.
He also identified another possibility: heavy rainfall in the Tibetan region of China may have triggered a massive landslide, forming a temporary natural dam that subsequently collapsed. Such an event, known as a landslide dam outburst flood, could have produced a sudden surge of water, mud and debris.
Upadhyaya said satellite imagery and further analysis would be needed to determine what actually happened. He noted that at least one of three glacial lakes located around 26 kilometers north of the Nepal-China border in the Tibetan region could potentially have contributed to the disaster. Another possibility, he said, was that an ice or landslide temporarily blocked the river before the accumulated water suddenly broke through.
A combination of events could also have produced the scale of destruction witnessed downstream, he said. A glacial lake outburst or landslide could have triggered a flood that swept away water and debris accumulated behind a lower temporary dam, creating a cascading disaster.
Upadhyaya warned that the risk may not yet be over if a landslide-created dam remains partially intact and a large volume of water and debris is still trapped upstream.
The National Disaster Risk Reduction and Management Authority and geologist Dan Shugar have presented preliminary evidence suggesting that a major landslide occurred in the Tibetan region and may have triggered the flood. However, Upadhyaya said an important question remained: where did the enormous volume of water, mud and rock that entered the river actually originate?
He called for a detailed scientific investigation into the possibility that the landslide and a GLOF may have occurred together. “The scale of destruction seen in this disaster would generally be difficult to explain through a single event,” he said, suggesting that a sequence involving an ice avalanche, glacial lake outburst, river blockage and sudden release of water could have occurred.
Meanwhile, the Chinese Embassy in Nepal has offered a different preliminary explanation.
Chinese Ambassador to Nepal Zhang Maoming said initial information indicated that an earthquake had occurred on the Nepali side on Wednesday morning, triggering an ice avalanche and subsequent mudslides. According to Zhang, the mudslides caused significant casualties and left people missing on both sides of the Gyirong-Rasuwagadhi border.
Talking to Nepal government national broadcast NTV, he said, “Following the disaster, the Chinese Embassy activated its emergency response mechanism, assessed the situation of Chinese citizens and businesses in the affected areas of Nepal, and requested the Nepali government and relevant authorities to intensify rescue operations. The embassy also dispatched a working team to the affected area to coordinate rescue efforts.” Despite casualties and losses on the Chinese side, China has also begun coordinating emergency supplies and cash assistance for Nepal, Zhang said.
He stressed the need for greater Nepal-China cooperation in disaster preparedness and response, including cross-border information sharing, monitoring and early-warning systems for meteorological, hydrological and geological hazards. He also called for stronger institutional coordination in emergency rescue, as well as greater cooperation in personnel training, technical exchanges and emergency supplies.
“Accusations help nothing; cooperation saves lives,” the Chinese Embassy said in a social media post.
The exact cause and sequence of events behind the Bhotekoshi flood, however, remain unclear. Experts say satellite imagery, hydrological data, geological assessments and information from both Nepal and China will be needed to establish what triggered the disaster.
