Hidden in the Himalayas, small glacial lakes are a deadly flood risk

On 8 July, floodwaters surged into the Bhote Koshi River along the Nepal-China border. At least nine people in the Nepali village of Rasuwagadhi were killed and dozens went missing. A major bridge connecting Nepal to China was swept away. The trigger for this devastating flood? A newly formed small lake on top of a glacier that was not visible before March this year.

Glacial lake outbursts are known to cause devastating floods, but these have typically been from larger and more well established lakes. Now, experts are finding that “tiny and short-lived glacial lakes are becoming more hazardous than previously perceived”, said Finu Shrestha, a remote sensing and geo-information analyst at the International Centre for Integrated Mountain Development – ICIMOD.

Among other reasons, the inability to monitor changes hidden beneath the surface of small glacial lakes means their potential impacts remain undiscovered. Further, when the lakes drain, even small releases can have big impacts downstream due to debris, the shape of river channels and other factors.

Fast forming, sensitive

What happened at Rasuwagadhi is not the first case of a glacial lake outburst flood from a smaller lake. In August 2024, a flash flood struck Thame village in eastern Nepal’s Solukhumbu district, in the Everest region, following a GLOF from Thyanbo Lake measuring only 0.05 sq...

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