Is glacial snout detachment at over 6,000 m reason for Dharali disaster?

Government authorities are examining whether a glacial snout detachment at over 6,000 m upstream of Dharali caused the flash flood, leading to immense devastation in Uttarakhand's Uttarkashi district on Tuesday.

It is suspected that a glacial snout at 6,700 m detached some days ago and large glaciofluvial debris deposits had collected at the site. Heavy rains over the past few days loosened the debris that cascaded downstream with water in Kheer Ganga, accelerating due to steep gradient up to Dharali, sources indicated. This has, however, yet to be corroborated with satellite imagery.

Glaciologist DP Dobhal told ET that while there is no clear evidence of the snout detachment, there was enough debris massed around it for several years now.


"One cannot conclusively say it was snout detachment until satellite imagery and ground assessment fully confirm so. Currently, the glacial sites are inaccessible but upwards of Kheer Ganga there are two unnamed glaciers which have seen significant accumulation of debris and old moraine, massing up over the years. There is also a hanging glacier just off the Kheer Ganga nallah that is to be closely watched. The river system itself may also have contributed. Also, even without a glacial snout detachment, very large debris flow may have impacted Dharali as the valley is quite narrow," Dobhal said. He, however, ruled out a Glof event since no such vulnerable lakes had been identified in the areas.

Government sources have also ruled out two other factors - cloudburst or even a glacial lake outburst flood (Glof).

No cloudburst was reported in the area as per sources, but there was heavy downpour that may have contributed to the detachment of the glacial snout and the consequent transport of glacial debris downstream in a flash flood.

As far as GLOF event is concerned, government assessment so far do not indicate such an activity in the state.

As per NRSC Atlas of 2023, there are 7500 glacial lakes greater than 0.25 ha in the Himalayas. Of these NDMA categorised 195 as at-risk. None of these are in the Dharali catchment.