Even when the scientists across the globe are yet to establish the exact turn of events that led to the disaster in Chamoli in February first week, recent satellite imagery has warned of a similar impending disaster.
A month after the disaster in Chamoli district of Uttarakhand that saw more than 70 dead and 130-odd missing, a premier global scientific organisation has warned that mass movement activities are still occurring in the zone where the initial rock and ice had failed in that high-altitude Himalayan region.
Massive flash flood was triggered due to breaking of a glacier in Nanda Devi massif leading to an avalanche in the Rishi Ganga valley above Joshi Math in Chamoli district on February 7. Two hydroelectric power projects – NTPC’s Tapovan-Vishnugad hydel project and the Rishi Ganga Hydel Project – were extensively damaged and the floods trapped several hundred labourers in the projects’ tunnels. More than three weeks later, as rescue operations continue, government has declared 72 people dead and 133 missing in the disaster.
Even when independent scientific and government’s environmental organisations are researching the exact cause of floods, there is some clarity now, thanks to satellite images.
Earlier, scientists had said that a major rock/ice avalanche detached itself at an elevation of about 5,600 m above sea level from a North facing slope Northeast of Trishul Peak in the Nanda Devi mountain. This caused the massive floods in the Rishiganga / Dhauliganga river.
Analysis of satellite imagery from the area show that this event occurred due to failure deep within the bedrock of the mountain, and the glacier ice was most probably entrained with the collapsing block of bedrock. The failing mass covered an area of around 0.2 km.Scientists working under the Glacier and Permafrost Hazards in Mountains (GAPHAZ) have found out.
GAPHAZ is a scientific standing group of the International Association of Cryospheric Sciences and the International Permafrost Association.
Historical imagery also indicate that a similar event has occurred in the neighbouring glacier just East of the current in September 2016, the analysis said, adding, “However, the initiation of the failure as well as the eventual trigger of the avalanche remain unclear. It is also important to note that unstable geological configuration and steep topography can, on its own, be a sufficient driver of large slope failures.”
But what the scientists have to say further from the in-depth analysis of satellite images is alarming. “Recent high resolution satellite imagery indicate that mass movement activities are still occurring in the zone where the initial rock and ice failed (on February 7). In case of another slope failure and avalanche, it can be critical for people and infrastructure downstream, close to the riverbed. It can be normal follow up activity of the main event, but it cannot be excluded that important secondary events can occur,” the study warned.
During the short tenure, high in intensity event on February 7, large volumes of material have been eroded from the mountains and deposited along the river channel. In combination with water from rivers, snow melt, heavy (monsoon) rainfall or overflow of temporary lakes, debris flows can be triggered from these depositions. “Erosion by the flood probably has undercut some slopes, and this instability could affect roads, villages and other infrastructure located far above the riverbed,” the study added.
Lauding the response to this disaster by the Indian and international science community as “extraordinary”, what with first analyses being provided within just about 24 hours, Dr Christian Huggel, Environment and Climate: Impacts, Risks and Adaptation (EClim), Glaciology & Geomorphodynamics, Department of Geography, University of Zurich, attributed it to the revolutionary developments in the satellite remote sensing over the past decades and coordination of the science community in international commissions such as GAPHAZ.
“While the Himalayan region is particularly prone to, and impacted by climate change, enhancing mass movement turn-over (such as sediment flux, or extreme events as in Chamoli), large slope failures (rock-ice avalanches) as in the case of Chamoli/Ronti Peak are often difficult to attribute to climate change. Such efforts need in-depth understanding and field and remote sensing data, for instance on geologic structure, permafrost occurrence and thermal distribution and perturbation, glacier decline history and mechanical stress changes in the affected steep slopes. Thorough investigation of the case will improve our understanding on all levels and hence provide the basis for targeted actions,” Dr Huggel said in a statement.
An analysis by the New Delhi-based Council on Energy, Environment and Water (CEEW) in February after the Chamoli disaster has revealed that more than 85% of districts in Uttarakhand, home to over nine crore people, are hotspots for extreme floods and its associated events. The frequency and intensity of extreme flood events in Uttarakhand have increased four-fold since 1970.
Similarly, associated flood events such as landslides, cloud bursts, glacial lake outbursts, etc. have also increased four-fold during this period, causing massive loss and damage. Chamoli, Haridwar, Nainital, Pithoragarh, and Uttarkashi districts are the most vulnerable to extreme floods, the CEEW study said.
According to a report on climate change released by the Ministry of Earth Sciences last year, the Hindu Kush Himalayas has experienced a temperature rise of about 1.3°C during 1951–2014. The increase in temperature has led to micro climatic changes and faster glacial retreat in Uttarakhand, thereby triggering frequent and recurrent flash floods.
Nivedita Khandekar is an independent journalist based in Delhi. She writes on environmental and developmental issues. She can be reached at firstname.lastname@example.org or follow her on twitter at @nivedita_Him