Ice patches on melting glaciers greater threat than thought: ISRO scientists

Researchers from the Regional (West) and National Remote Sensing Centres of ISRO have found that the presence of exposed ice patches on the Srikanta Glacier immediately before the floods of August 5 was a signal of ongoing deglaciation and a direct indicator in the landscape of the likelihood of such floods.

A new study by scientists from the Indian Space Research Organisation (ISRO), published in NPJ Natural Hazards, examines the August 5, 2025 flash flood that destroyed Dharali village in Uttarakhand and killed six people. It sheds light on how warming temperatures affect glaciers, especially exposed ice patches on retreating glaciers, and highlights the need to monitor glaciers using satellite images to provide early warnings of possible disasters.

The study, titled ‘Ice-patch collapse and early-warning implications from a Himalayan flash flood: emerging cryo-hydrological hazards under deglaciation’, concludes that the collapse of an ice patch on the glacier above Dharali is linked to deglaciation in the Himalaya.

The authors say the findings could help improve understanding of climate risk and disaster preparedness. The study shows that the flash flood was triggered by the collapse of an ice patch in the nivation area of the Srikanta glacier.

Nivation is defined as the erosion of the ground beneath and around a snow bank, primarily as a result of alternate freezing and thawing. This can form a nivation hollow, which gradually becomes deeper when snow repeatedly accumulates in the same place.

The study area lies in the upper Bhagirathi river basin in Uttarkashi district of Uttarakhand. It covers the ridge-to-valley system from the Srikanta glacier to Dharali village, located at a height of 2,650-2,700 m along the Bhagirathi river. The village lies downstream of the glacier-fed Khir Gad stream, which originates from the Srikanta glacier, flows through Dharali, and then joins the Bhagirathi river. The Khir Gad divides Dharali into right- and left-hand bank settlements, increasing its risk of flash floods.

The region has a documented history of extreme events, including the large landslides that brought down massive boulders during the June 2013 Himalayan floods. The researchers used satellite observations, high-resolution topographic analysis, and visual records to reconstruct the sequence of events linking unstable glacier ice to the sudden flood.