Last Updated:March 07, 2026, 16:05 IST

ISRO study revealed the flood was triggered by the sudden collapse of an exposed ice patch within the nivation zone of the Srikanta Glacier.

In a recent study, scientists from the Indian Space Research Organisation (ISRO) have pinpointed an overlooked hazard in snow-covered areas as the cause of the flash flood that ravaged parts of Uttarkashi in August 2025.

The devastating flash flood in Dharali, located in the Uttarkashi region of the Central Himalayas, led to significant damage and loss of life. According to the study, the flood was triggered by the sudden collapse of an exposed ice patch within the nivation zone of the Srikanta Glacier.

Nivation zones are areas in high mountains where glaciers undergo seasonal freezing, thawing, and meltwater movement. These processes break down rocks and transport debris, often resulting in the formation of steep-walled, bowl-like basins due to erosion.

What Does ISRO Study States?

Seven months after the massive devastation, ISRO’s detailed satellite imagery analysis revealed sudden collapse of a massive, unstable ice patch as the trigger for the tragedy. It ruled out the possibility that the catastrophe was a conventional meteorological event.

The ISRO report describes how around 6.9 million kilograms of ice cascaded down the slopes. As this large mass of frozen material moved, friction transformed it into a high-speed mixture of ice and meltwater.

Satellite images from July 2025, before the incident, showed an exposed ice patch at an elevation of 5,220 metres, a feature not seen in 15 years of recorded data.

Images taken after the event on August 12 confirmed that this patch had disappeared, leaving behind deep, fresh erosion scars on the slope.

Scientists Issue Warning

The report clarifies that the disaster was not a typical Glacial Lake Outburst Flood (GLOF), as no such lake existed in the upper catchment basin. Furthermore, rainfall data between August 3 and 5 recorded only light to moderate precipitation, ruling out cloudbursts.

“The pattern of the flood, a sudden, high intensity surge followed by a prolonged, low intensity flow, is a hallmark of a mass release event," an excerpt from the report reads.

The study highlights the changing climate of the Himalayas as a cause for concern. Scientists clarified that an “ice patch" is a static mass comprising snow, firn, and layered ice, rather than a moving glacier.

With global temperatures increasing and snowfall patterns becoming unpredictable, these patches lose their protective layers, making them mechanically unstable and susceptible to sudden collapse.

“This event represents an emerging class of cryo-hydrological hazards," the scientists cautioned. The report also notes the limitations of optical satellites during the monsoon season, when cloud cover often hinders surveillance.

News india 2025 Uttarkashi Flash Flood Triggered By Ice Patch Collapse, Not Cloudburst: ISRO Study

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