Context
- A study by scientists from the Indian Space Research Organisation, published in the journal NPJ Natural Hazards, analysed the 5 August 2025 flash flood in Dharali village, Uttarakhand that destroyed settlements and caused casualties.
- The research concluded that the disaster was triggered by the collapse of an exposed ice patch on the Srikanta Glacier, highlighting new forms of climate-induced cryospheric hazards emerging in the Himalaya.
- The findings emphasise the importance of satellite monitoring and early-warning systems to detect glacier instability and prevent disasters in high-altitude regions.
Relevance
- GS III – Environment / Climate Change: Demonstrates climate-induced cryospheric hazards in the Himalaya, including glacier instability and flash floods.
- GS III – Disaster Management: Highlights the role of satellite monitoring and early warning systems in managing glacier-related disasters.
Practice Question
- “Climate change is increasing the frequency and diversity of cryospheric hazards in the Himalayan region.”Discuss the emerging glacier-related risks in the Himalaya and the role of technology in disaster preparedness.(250 Words)
Static Background: Himalayan Cryosphere
What is the Cryosphere?
- The cryosphere refers to the frozen components of the Earth system, including glaciers, snow cover, ice caps, sea ice, permafrost and frozen ground.
- The Himalayan cryosphere, often called the “Third Pole”, stores the largest volume of ice outside the polar regions and feeds major Asian river systems.
Importance for India
- Himalayan glaciers sustain the headwaters of rivers such as the Ganga River, Brahmaputra River and Indus River, supporting water security for millions of people.
- Rapid glacier retreat due to climate change increases the frequency of cryospheric hazards, including glacial lake outburst floods (GLOFs), ice avalanches and flash floods.
Location of the Dharali Flash Flood Event
- Dharali is located in Uttarkashi District, Uttarakhand, along the upper basin of the Bhagirathi River, a major headstream of the Ganga.
- The village lies at an altitude of approximately 2,650–2,700 metres, downstream of the Khir Gad stream, which originates from the Srikanta Glacier.
- The Khir Gad stream divides the settlement into left-bank and right-bank clusters, increasing vulnerability to flash floods triggered upstream in the glacier-fed basin.
Key Scientific Findings of the Study
Trigger Mechanism of the Flood
- The flash flood was caused by the collapse of an exposed ice patch in the nivation zone of the Srikanta Glacier, which released ice, meltwater and debris downslope.
- The sudden release of this material generated a rapid cryo-hydrological event, producing a flash flood that travelled downstream through the Khir Gad stream into Dharali village.
Evidence from Satellite Observations
- Pre-event satellite imagery revealed persistent exposed ice patches during the ablation season, indicating thinning seasonal snow and firn layers due to ongoing glacier retreat.
- These exposed patches acted as structural weak points, making them more vulnerable to collapse during periods of warming temperatures or heavy rainfall.
Deglaciation Signal
- The study identified the exposure of ice patches as a landscape indicator of deglaciation, reflecting the weakening of protective snow and firn layers on the glacier surface.
Key Cryospheric Concepts
Nivation
- Nivation refers to the erosion of the ground beneath or around a snow patch caused by repeated cycles of freezing and thawing, along with meltwater action.
- Over time, this process creates a nivation hollow, a depression where snow accumulates repeatedly and gradually deepens due to erosion and weathering.
Firn
- Firn is partially compacted snow that has survived at least one melt season and represents an intermediate stage between fresh snow and glacial ice.
- Firn acts as an insulating layer, protecting underlying glacier ice from rapid temperature fluctuations and structural instability.
Ablation Zone
- The ablation zone of a glacier is the region where melting, sublimation and ice loss exceed snow accumulation, leading to net mass loss of the glacier.
Mechanism of Ice Patch Collapse
- Normally, seasonal snow and firn layers stabilise glacier surfaces by insulating underlying ice and reducing temperature fluctuations.
- With climate warming, thinning snow cover exposes glacier ice directly to atmospheric conditions, making it more susceptible to melting, fragmentation and collapse.
- Exposed ice patches respond quickly to temperature changes, rainfall and gravitational instability, potentially triggering sudden mass movements of ice, water and debris.
Cryo-Hydrological Hazards in the Himalaya
Expanding Hazard Spectrum
- Traditionally, glacier hazards in the Himalaya were associated mainly with Glacial Lake Outburst Floods (GLOFs).
- The Dharali event demonstrates that smaller cryospheric instabilities such as ice-patch collapse, rock-ice avalanches and debris flows can also trigger destructive floods.
Historical Example
- The 2021 Chamoli Disaster involved a massive rock-ice avalanche in Uttarakhand that caused flash floods in the Rishi Ganga and Alaknanda river systems.
- Such events highlight increasing instability in Himalayan glacier environments under conditions of rapid warming and glacier retreat.
Role of Satellite Monitoring
Earth Observation Technologies
- Satellite imagery, high-resolution topographic mapping and remote sensing data allow scientists to identify glacier instability, exposed ice patches and changes in snow cover.
- Continuous monitoring of glaciers using satellite-based earth observation systems can detect early warning signs of potential cryospheric hazards.
Early Warning Potential
- Pre-event satellite observations in the Dharali case revealed persistent exposed ice patches before the flood, demonstrating their potential as indicators for disaster preparedness.
- Integrating satellite monitoring with ground-based sensors and hydrological models can improve early-warning systems for mountain communities.
Environmental and Climate Dimension
- Rising temperatures in the Himalaya are causing accelerated glacier retreat and thinning of seasonal snow cover, altering the stability of mountain cryospheric systems.
- Climate-driven deglaciation is increasing the frequency of flash floods, landslides and glacial hazards in fragile mountain ecosystems.
- The Himalayan region is warming faster than the global average, intensifying the risk of downstream disasters in glacier-fed river basins.
Disaster Risk and Governance Challenges
Limited Monitoring Coverage
- Many Himalayan glaciers remain poorly monitored due to difficult terrain, remoteness and limited ground-based instrumentation.
Early Warning Gaps
- Existing early-warning systems focus primarily on GLOFs, while smaller cryospheric instabilities such as ice patch collapse often remain undetected.
Settlement Vulnerability
- High-altitude villages located along glacier-fed streams face high exposure to flash floods, debris flows and landslides, requiring stronger disaster preparedness.
Way Forward
Systematic Glacier Monitoring
- Expand satellite-based glacier monitoring programmes led by ISRO and national research institutions to identify vulnerable glacier zones across the Himalaya.
Hazard Mapping
- Conduct geomorphological mapping of nivation hollows, exposed ice patches and unstable glacier slopes to identify potential flash flood sources.
Integrated Early Warning Systems
- Combine remote sensing data, hydrological models and local monitoring networks to establish real-time early-warning systems for mountain communities.
Climate Adaptation Planning
- Strengthen climate-resilient infrastructure and disaster preparedness strategies in Himalayan regions vulnerable to glacier-related hazards.
Research Collaboration
- Encourage collaboration between ISRO, glaciology institutes and international climate research programmes to improve understanding of cryosphere dynamics.
Prelims Pointers
- Cryosphere: Frozen part of Earth including glaciers, ice sheets, snow cover and permafrost.
- Nivation: Erosion beneath a snow patch due to freeze–thaw cycles.
- Firn: Intermediate stage between snow and glacial ice.
- Ablation zone: Area of glacier where melting exceeds accumulation.
- Third Pole: Himalayan–Tibetan region containing the largest ice reserves outside polar regions.
