A new study by scientists from the Indian Space Research Organisation (ISRO), published in NPJ Natural Hazards, examines the flash flood (August 2025) that destroyed Dharali village in Uttarakhand.
- The Study concludes that the collapse of an ice patch on the glacier above Dharali is linked to deglaciation in the Himalaya.
- Area of Study: It 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 along the Bhagirathi river.
About Srikanta Glacier
- Location: Srikanta Glacier is a small to medium-sized valley glacier with a height of 6,133 m, around 9.8 km upstream of Dharali.
- The glacier has steep accumulation and ablation zones, seasonal snow cover, and extensive nivation areas.
- Terrain: Situated in a high-altitude Himalayan region with steep slopes and active glacial processes.
- Hydrology: Feeds the Khir Gad stream, which flows through Dharali village and later joins the Bhagirathi River.
- Glacial Characteristics: A retreating Himalayan glacier affected by warming temperatures and ongoing deglaciation.
About Dharali Village
- 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.
About Ice-patch Collapse
- It refers to the sudden breaking or detachment of a small exposed mass of glacier ice, often located on steep slopes or in the nivation zone of a glacier.
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Key Findings of Study
- Cause of Flash Flood: Flash flood was triggered by the collapse of an ice patch in the nivation area of the Srikanta glacier.
- Research Methodology: 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.
- Expansion of Glacier Hazard Understanding: The findings expand the range of recognised glacier-related hazards in the Himalaya and identify exposed ice patches as an under-recognised risk from glacier melt.
- Need for Broader Hazard Monitoring: The study calls for closer monitoring of glaciers and argues that the focus should extend beyond glacial lake outburst floods (or GLOFs) to include smaller, often overlooked instabilities in the cryosphere.
- Risk from Exposed Ice: Ice patches covered by firn and seasonal snow are relatively resistant to short-term temperature changes whereas exposed ice is more likely to shift or loosen.
About Nivation
- Nivation is defined as the erosion of the ground beneath and around a snow bank, primarily as a result of alternate freezing and thawing.
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- Evidence from Pre-Event Imagery: Pre-event imagery during the ablation period revealed exposed ice patches on steep north- to northeast-facing slopes, indicating thinning seasonal snow and firn cover consistent with ongoing deglaciation
- Impact of Warming Temperatures: It sheds light on how warming temperatures affect glaciers, especially exposed ice patches on retreating glaciers.
- Importance of Satellite Monitoring: It highlights the need to monitor glaciers using satellite images to provide early warnings of possible disasters.
Significance
- Helpful in Disaster Preparedness: It could help improve understanding of climate risk and disaster preparedness.
- Early Warning System: It shows the value of pre-event satellite observations for early warning.
- Satellite images showed exposed ice patches persisting in the nivation zone during the ablation period, when the glacier loses ice and snow.
16 Mar 2026
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