Uttarkashi’s Dharali disaster: If not a cloudburst, then what? Met, satellite data point to another cause

Uttarkashi flash floods (AFP)

The devastating flash flood that swept through Dharali village in Uttarakhand’s Uttarkashi district on Tuesday may have been caused by a glacier collapse or glacial lake outburst, rather than the initially suspected cloudburst, according to experts analysing satellite images and weather data, The Times of India reported.

Although the disaster, which hit around Tuesday afternoon, was initially believed to have resulted from intense rainfall, meteorological data from the Indian Meteorological Department (IMD) does not support this theory. IMD recorded only light rain in the area, 6.5 mm in Harsil and 11 mm in nearby Bhatwari, which is quite below the threshold typically associated with cloudburst-induced flooding.

"Only very light to light rain was observed in the affected area over 24 hours. The highest rainfall recorded anywhere in Uttarkashi was merely 27mm at the district headquarters,” TOI quoted Rohit Thapliyal, senior scientist at IMD's regional meteorological centre, as saying.

Another scientist added, “This pattern suggests that a major geophysical event, such as a glacial lake outburst flood (GLOF) or a glacier collapse, may have triggered the flash flood.”

As per TOI, the satellite images showed the presence of significant glaciers and at least two glacial lakes situated upstream of the disaster site. One such glacier lies directly above the Kheer Gad stream, which runs through Dharali. According to the experts, a sudden release of water from this glacier or one of the lakes could have led to a massive surge, similar to the 2021 Raini disaster in Chamoli. That incident involved a rock-ice avalanche that destroyed two hydropower plants and claimed over 200 lives.

Uttarakhand is home to over 1,200 glacial lakes, several of which pose a serious risk to communities located downstream. According to the Wadia Institute of Himalayan Geology and the National Disaster Management Authority (NDMA), at least 13 of these lakes have been classified as “high-risk,” with five considered extremely dangerous.

Senior geologist and former executive director of Uttarakhand Disaster Management Authority Piyoosh Rautela said, "Such disasters occur when water accumulates at higher elevations and discharges suddenly... Heavy rainfall alone can't cause such a disaster."

The impact on the ground has been severe. At least four people have been confirmed dead, and many more, possibly up to 70, are feared missing. Among them are nine Indian Army personnel who were at a camp near Dharali, around 4 km from Harsil along the Gangotri highway, according to a report by The Hindu.

Video footage captured by residents shows terrifying scenes of muddy waves sweeping through Dharali, a picturesque town located 8,600 feet above sea level. People can be heard shouting warnings as the floodwaters tore through buildings, markets, and homes. Within minutes, the popular tourist spot was reduced to a slushy wasteland.

According to initial estimates, the flood destroyed at least 25 establishments, including hotels, guesthouses, and private homes. Rescue and relief operations are still underway as teams continue to search for the missing, Hindustan Times reported.