ICE PATCHES ON MELTING GLACIERS IN THE HIMALAYAS

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Picture Courtesy:  THEHINDU

Context

A recent study on the Dharali village flash flood (Uttarakhand, August 2025) by the Indian Space Research Organisation (ISRO) has identified a new and dangerous cryo-hydrological hazard. 

What are the key Findings of the Study?

A collapse of an exposed ice patch in a 'nivation' area, rather than a traditional Glacial Lake Outburst Flood (GLOF), caused the flood. This highlights a previously overlooked threat linked to rapid Himalayan deglaciation.

The Collapse is driven by:

Nivation

It is a localized erosion process where repeated freeze-thaw cycles beneath snowbanks carve out depressions known as nivation hollows.

Protective Role of Firn

In healthy glaciers, a protective layer of firn and seasonal snow acts as insulation, shielding the underlying ice from atmospheric temperature fluctuations and preventing rapid melting.

The Collapse Trigger

Rising temperatures during the melting season strip away protective snow layers, leaving exposed ice patches to react instantly to heat and rain, causing rapid fragmentation and sudden collapses that trigger violent debris-laden flash floods.

What is the nature of the escalating threat in the Himalayas?

The Dharali incident signals a systemic risk driven by accelerating climate change, moving beyond the traditionally monitored Glacial Lake Outburst Floods (GLOFs).

Accelerated Deglaciation

Glaciers in the Hindu Kush Himalaya (HKH) region disappeared 65% faster in the 2011–2020 decade compared to the previous one. Projections indicate a potential loss of up to 80% of glacier volume by 2100 under current emission scenarios. (Source: ICIMOD HI-WISE Report)

Global Ice Loss

The period from 2022 to 2024 saw the largest three-year loss of glacier mass on record globally, confirming a worsening trend. (Source: WMO State of the Global Climate Report)

Expanding the Hazard Matrix

While disaster management historically prioritizes GLOFs, the collapse of unstable ice patches in nivation hollows represents an equally destructive but under-monitored "transitional state" of glacial retreat

What are the potential impacts?

Sudden cryospheric failures cause severe cascading impacts downstream, devastating both local populations and critical infrastructure.

Key Case Studies of Disasters

Threat to Regional Water Security

Glacier collapse and rapid melting disrupt stable water supplies, causing flash floods and chronic seasonal droughts, threatening water and food security for millions in India and Pakistan.

Mitigation and The Way Forward

Mandate Pre-Event Satellite Surveillance

The ISRO study confirms that high-resolution satellite imagery can identify exposed ice patches before they fail. High-resolution satellite data must be used to map nivation hollows as a standard procedure.

Update NDMA Guidelines

The National Disaster Management Authority's (NDMA) National Glacial Lake Outburst Floods Risk Mitigation Programme (NGRMP) must be expanded to include the mapping and monitoring of "geomorphologically sensitive nivation zones" and other unstable ice surfaces.

Adopt Global Best Practices: India can learn from international models:

• Switzerland (GLAMOS): Uses 3D laser scanning and in-situ sensors to monitor micro-changes in glaciers and feed data directly into local early warning systems.
• Canadian Arctic Protocols: Explicitly include ice-patch collapse in their hazard mapping, recognizing its distinct and rapid trigger mechanism.

Enforce Strict Land Use Planning

To prevent settlement expansion into vulnerable areas, state governments must enforce NDMA construction prohibitions in high-risk zones using Digital Elevation Models (DEM) to map potential flood paths from all glaciated peaks.

Conclusion

The Dharali flash flood signals an urgent need for India to shift from reactive responses to predictive monitoring by institutionalizing satellite surveillance of nivation zones and updating national risk frameworks to mitigate the growing threat of exposed ice patch collapses.  

Source: THEHINDU