On 21 April 2024, a flood from the glacial lake Birendra Tal was triggered by a massive ice avalanche caused by calving from the Manaslu Glacier. Manaslu, the eighth-highest mountain in the world at 8,163 meters above sea level, is located in west-central Nepal. The displacement wave resulted in the sudden release of water from the lake outlet into the Budhi Gandaki River in Gorkha district. This event was not a typical glacial lake outburst flood (GLOF), as the overflows did not breach the moraine dam, and no significant impact on the dam was observed post-event.
However, the threat remains. Analysis indicates a significant risk of debris flow and ice/snow avalanches from the adjacent valley, compounded by anticipated temperature rises and glacier retreat, suggesting future occurrences could exceed the moderate impact of this event. Vigilance from Disaster Risk Management Officers, community leaders, and governments is recommended.
A detailed understanding of glacier dynamics, crevasse formation, and ice detachment processes is crucial for assessing potential risks. Remote sensing techniques and field-based monitoring, such as GB-InSAR and time-lapse cameras, can provide necessary information. Continuous lake monitoring via satellite imagery and in-situ sensors, along with the establishment of a flood early warning system, is recommended to mitigate risks and enhance preparedness.
Weakening glaciers in the region pose various hazards, and countries remain ill-prepared to cope with these rapid changes. Urgent and strong political action is required to implement effective risk mitigation strategies.