When a mountain falls: How ice and rock triggered Nepal’s catastrophic flood – and why climate change is raising the risks
A geologist explains how thawing permafrost and melting ice are increasing the risk of destructive floods in the Himalayas and other high mountain regions around the world.
A massive rockfall in the Himalayas triggered a catastrophic flood that killed hundreds of people in Nepal on August 26, 2026. The disaster began when ice and rock tumbled from a slope north of Langtang Lirung, crashing into a valley 4,000 feet below. This landslide generated a slurry of water, ice, and debris that flowed rapidly into the river.
According to satellite and seismic data, the initial landslide shook the earth with a magnitude 5.2 earthquake. The resulting water surge inundated nearby towns, causing widespread destruction and claiming many lives. Within a day, a new "barrier lake" formed behind debris where two rivers converged in Tibet before crossing into Nepal.
This lake burst open on August 28, causing another wave of flooding. The combination of initial landslide, dammed river, and bursting lake resulted in extensive damage to infrastructure, including hydropower plants, bridges, and the Gyirong Port border crossing. Scientists attribute the increased flood risk to climate change, which has accelerated snow and glacier melt, creating more glacial lakes and destabilizing permafrost.
As the planet warms, the risk of such disasters in high mountain regions around the world is expected to rise.
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