A major flood hit Nepal’s Rasuwa district just after midnight and has been traced to a collapse of frozen ground (permafrost) in the upper part of the Lhende River, located in China’s Tibet region.

Nepal’s weather and geology experts, with help from satellite images and local officials, confirmed that a chunk of long-frozen land suddenly gave way near the river’s source. This triggered a massive flood that flowed into Nepal through the Gosainkunda area.

Permafrost is ground that stays frozen all year. Even small amounts of rain or rising temperatures can melt it, leading to floods or landslides. The Lhende River, which is called Bhote Koshi in Nepal, starts in Tibet and is fed by glaciers. It joins the Trishuli River downstream. The flood destroyed the Nepal-China Friendship Bridge at Rasuwagadhi.

There are at least seven glacial lakes on the Tibetan side and one small lake in Nepal that feed into this river. Warmer weather and more rain in recent years have been melting this frozen ground, which can cause the land to collapse and flood suddenly.

This process also creates holes under the ground, called “thermokarst,” which can fill with rainwater and then break, leading to dangerous floods. A similar event happened in August in Thame, Solukhumbu, when melted permafrost caused a glacial lake to burst.

In the days before the Rasuwa flood, there was only light rain in the area, but temperatures rose enough to destabilize the permafrost. Experts say that even small increases in temperature and rain can lead to huge floods in mountain rivers.

Prime Minister KP Sharma Oli visited the disaster site by helicopter, but only after the damage was done. Critics say the government has failed to prepare for climate-related disasters in the mountains.

Experts warn that rising temperatures and rainfall are increasingly causing dangerous events like glacial lake bursts, glacier melting, and permafrost collapses. Even Tibet is now getting monsoon rains, and these changes are reducing rainfall in southern Nepal.

Satellite images showed no major rainfall or clouds over the flood area at the time of the disaster, suggesting earlier rains and warming were enough to trigger the flood.

Nepal has over 6,000 rivers. Many of them begin in the Himalayas or in Tibet. When these rivers flood, the damage can stretch from the mountains to the plains, especially along riverbanks and valleys.

Unusual rainfall has been seen in Nepal’s Himalayan areas for about 10 years. Much of Tibet’s water flows into Nepal. Warmer weather and more rain are now melting the once-frozen mountains, increasing the risk of disasters like this.