Did a glacial lake breach trigger the Dharali disaster? Experts find some clues

If a lake had indeed formed recently, it could have been breached due to movements in glacier mass, said Kulkarni, a distinguished scientist at Divecha Centre for Climate Change, Indian Institute of Science.

“The Kheer Ganga originates from glaciated terrain and September 2022 imagery shows that snow was melted, and one can clearly see landforms. A well-developed deglaciated valley can also be seen. This deglaciated valley is bounded by end moraine and a small river is passing between the end moraine and a side wall,” he said.

An end moraine is typically the far or end portion of a glacier mass and is made up of rocks, debris and sediments. Kulkarni said a meandering stream was above the end moraine, indicating terrain that could have seen lake formations in the past.

Kulkarni said there were indications that the lake might have formed due to a landslide from the end moraine. “The (Dharali) flash flood of mud flow might have been caused due to an outburst of the lake. This could also explain past floods in the Kheer Ganga River. The channel is very steep and hence it must have crashed down quickly,” he said.

Glacial lakes are usually formed when meltwater from glaciers accumulates in terrains that are eroded or naturally dammed by movement of glaciers.

In the recent glacial lake outburst flood events, such as the South Lhonak lake incident in Sikkim in October 2023, about 14.7 million cubic metres of mass of ice, rock and sediments crashed into the lake, sending water, equal to 20,000 Olympic-sized swimming pools, crashing downstream.

Past analysis has shown, like in the case of the Kedarnath disaster, that there was a moraine dam that held together the Gandhi Sarovar or Chorabari lake above Kedarnath, Kulkarni said.

Officials from the National Disaster Management Authority (NDMA) said they were looking at a possible detachment of a glacial snout (the nose where glacier breaks) that could have carried massive quantities of debris downstream.

However, the officials added that they were coordinating with the National Remote Sensing Centre (NRSC) to analyse sharper images of the period leading up to the disaster.