On the morning of 26 August 2026, a series of flash floods and debris flows destroyed the Gyirong Port on the China–Nepal border and struck dozens of settlements along a 72 km (45 mi) stretch of the Trishuli River in Nepal. These events are also known as the 2026 Nepal-China floods, Bhotekoshi flood, or Rasuwa flood.
At least 1,455 deaths and 5,285 missing persons in Nepal, and 43 deaths and 519 missing in the Tibet Autonomous Region of China were reported. The flood carried the bodies of some victims 250 km (160 mi) away into neighbouring India.
The precipitating geological event, initially reported as a glacier collapse in the Langtang region of the Himalayas, caused a chain reaction whose tremors were detected by seismometers worldwide, with magnitudes reaching Ms 5.2. According to experts at the National Society for Earthquake Technology–Nepal (NSET), the University of Reading and Newcastle University, the flood was triggered by a large rock-ice avalanche originating from the Lirung massif, involving glacier ice and rock, which transformed into a highly mobile, long-runout debris flow and generated destructive downstream flooding.
The Trishuli River is joined by the Lhende Khola (also known as Lende River or Donglin Tsangpo in Lhasa Tibetan), which originates in Gyirong County, Tibet Autonomous Region before entering Nepal. It then flows past Dhunche, downstream from which it forms part of the Trishuli River system.
The flash floods and mudslides occurred around the China–Nepal border crossing at Gyirong Port, a strategic border crossing connecting Nepal's Rasuwa District and Gyirong County, located at the confluence of the Trishuli and Lhende Khola rivers. The crossing saw large amounts of daily traffic related to both commerce and tourism, especially the pilgrimage tour to Mount Kailash, a holy site in Bon, Buddhism, Hinduism and Jainism. The Gyirong crossing accounted for 30% of all Nepal-China trade before the disaster, and more than 100,000 people had used the crossing in the first half of 2026 according to Chinese media.
Since 1900, dozens of floods have occurred near the border between Nepal and China. Langtang Lirung, opposite the site of the 2026 landslide, experienced a major glacier collapse and debris avalanche triggered by the April and May 2015 Nepal earthquakes. The landslide in the Langtang valley destroyed and buried several villages, killing over 350 people. A July 2025 flood caused by a glacial lake outburst washed away the bridge at the border crossing.
Analysis of satellite imagery found that from 8 January 2026 to 18 August 2026, the glacier north of Langtang Lirung moved around 10 millimetres per month, but the rate accelerated in the weeks prior to the glacier's collapse.
Climate change contributes to the melting of permafrost, which in turn increases the likelihood of glacier collapses. Alton C. Byers, a senior research associate at the Institute of Arctic and Alpine Research, University of Colorado Boulder, said, "Permafrost has been the cryospheric glue that's held the rock and the ice and the glaciers together for millennia, and now we're getting increasing evidence that it's being weakened by warming trends."
Researchers quoted by the BBC, CNN, and NPR said climate change probably increased the likelihood of the event. Nepal foreign minister Shisir Khanal called for increased global response to climate change and stated that Nepal was bearing a disproportionate share of its consequences.
Chinese and Nepali scientists have maintained a flash flood early warning system for years, which the South China Morning Post credited with consistently preventing casualties. The system did not detect the August 2026 flood in time as the water level monitors were configured for detecting monsoon and perennial floods. Upstream monitoring stations in Nepal were swept away by the flooding before alerts could be sent. A senior fellow at the Stimson Center remarked that the affected region was a monitoring "blind spot" and that geologists paid little attention to it.
After the 2025 floods, Chinese authorities in Gyirong County took a number of measures in preparation for a new glacial lake outburst flood. The local government updated emergency plans, set up a sentry system monitoring water level changes, constructed flood prevention structures such as a new flood wall, dikes and channels, trained local officials in "glacial lake outburst defense", and simulated an emergency evacuation of villagers. The August 2026 flood, which was caused by a different event than the system was built to anticipate, overwhelmed these defenses within minutes.
The incident began at around 08:37 NPT. At 09:00, the Nepalese Department of Hydrology and Meteorology was informed of the flood by the District Administrative Officer in Rasuwa, by which time several communications towers had been destroyed and door-to-door warnings were being sent. The first text alerts were sent out by 09:15, with 679,295 warning text messages sent within one minute. Authorities issued flood warnings for communities along rivers in the Nepali districts of Rasuwa, Nuwakot, Dhading, Gorkha, and Chitwan.
No rain was reported on the morning of 26 August at the Rasuwa district headquarters.
A seismic event measuring Ms 5.2 occurred at 02:52 UTC (08:37 NPT; 10:52 BJT) and was centred just north of Langtang Lirung, a mountain in Langtang National Park. The seismic event was initially believed to be an earthquake; later analysis by the United States Geological Survey (USGS) indicated that the seismic event did not precede the collapse but was rather generated by the collapse itself. The USGS' analysis found that the long-period seismic waves were consistent with a glacier collapse. The GFZ Helmholtz Centre for Geosciences (GFZ), in Potsdam, Germany, recorded an event measuring Mw 5.7 that was consistent with a landslide with a timestamp identical to the USGS. Other early analyses suspected a glacial lake outburst flood (GLOF).
A second landslide event was identified by USGS three hours after the first by analyzing low-frequency seismic waves. The second landslide was recorded as a Ms 4.2 seismic event.
Seven minutes after (vis. 2026 Nepal floods timeline) the seismic event, a surveillance camera captured floodwaters destroying the Gyirong Port border crossing. Geomorphologists quoted by the BBC and NPR proposed that the collapsed portion of a glacier fell thousands of metres and melted from the velocity and friction of the impact. The meltwater and rocks then displaced the river in the valley.
There were indications of heavy water flow almost immediately after the seismic waves were detected. The combination of the two near-simultaneous signals, and review of the first satellite imagery, led researchers to conclude that a glacier located around 64 kilometres (40 mi) north of the capital city Kathmandu and some 15 km (9.3 mi) east of where the flood was first noticed, measuring 600 metres (2,000 ft) in width may have fallen 1,200 metres (4,000 ft), in what is known as a glacier collapse (also called an ice avalanche). According to Daniel Shugar, a geologist at the University of Calgary in Canada who reviewed satellite imagery after the event, a 0.2 km2 (49-acre) piece of ice and rock broke off at about 5.2 km (3.2 mi) above sea level and fell vertically about 1.2 km (0.75 mi) to the valley below.
Satellite images and seismology confirm that a glacier collapsed near Langtang Lirung, which itself is a likely result of destabilisation by tectonic uplift and climate warming. Compared to GLOFs, glacier collapse floods are less frequent in the region, but more destructive. The collapsed glacial material was believed to have originated from an altitude of 5,200–5,400 m (17,100–17,700 ft) and had a size of around 197×10^6–492×10^6 m3 (7.0×10^9–17.4×10^9 ft3). It then moved north-westwards before shifting west.