New lake forms above Rasuwa after avalanche, raising flood concerns

A significant natural dam has formed, creating a large lake below a massive avalanche on Langtang Lirung in northern Nepal, sparking fears of further flooding in the Rasuwa district.

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It appears that a mass of snow and ice fell from around 5,000 metres to an elevation of around 3,000 metres. Because it came crashing down from such a height, we estimate that it generated enormous energy.

The avalanche, which occurred on Wednesday morning, sent a mixture of ice, snow, and rock cascading down the mountain. Experts estimate the debris fell from approximately 5,500 meters to around 3,000 meters, generating immense energy. This mass is believed to have flowed downhill, creating a depression where water has accumulated, forming the new lake.

Chinese media, citing the country's Ministry of Water Resources, reported that around 2 million cubic meters of water had pooled by Thursday. Chinese state television has warned that the volume could increase to approximately 3 million cubic meters in the coming days. The lake is situated below the Chhochen Khola and Purepu Tsangpo rivers, whose waters feed into the Lhende Khola, eventually reaching the Kerung Khola near the Rasuwagadhi border crossing.

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The risk of the natural dam breaking and causing another major flood remains.

Nepal's National Disaster Risk Reduction and Management Authority (NDRRMA) has confirmed the lake's formation and expansion, noting that satellite images show the Lhende Khola's flow has been blocked. While the authority has urged residents in downstream areas to remain vigilant due to the risk of the natural dam breaking, experts suggest that a potential flood from this lake might not reach the scale of the initial avalanche disaster. However, the expanding lake has undeniably heightened concerns about the possibility of another major flood.

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If the lake bursts, the flood from there will not be like Wednesday’s.