New lakes near Nepal, China border add to flood concerns amid hunt for avalanche trigger

Scientists and disaster agencies investigated the cause of the deadly Nepal flash floods that struck on August 26. The leading theory remains an ice-rock avalanche, but the trigger remains under examination. The US Geological Survey (USGS) revised its initial reading of the event from a magnitude 4.4 earthquake to a magnitude 5.2 landslide.

The tremor that officials in Kathmandu initially suspected of triggering the flood was actually the collapse itself. Two lakes formed upstream on the Lhende Khola after the debris flow blocked the river's course, posing a high risk of a major flood downstream. China warned of 3 million cubic meters of water expected to flow into an already dammed lake on its side, creating a high risk of a breach.

Experts have identified a pattern of vulnerability across the Hindu Kush Himalaya region, with four of the eight countries recording more than 10 major disasters in 2025, including landslides, floods, and glacial lake outburst floods (GLOFs). The Langtang catchment in Nepal has been warming rapidly, with glacierized areas above 4,000 meters warming at 0.31°C per decade, leading to a 40% loss of ice cover since the Little Ice Age.

This fragmentation and disconnection of high-elevation ice is now the dominant mode of glacier retreat in the region, posing significant geohazards.