Studies, including the recent space satellite images shared by ISRO, have found that the town has been sinking for a while
This article is part of a special edition on the Himalayas, published in February 1-15, 2023, issue of Down To Earth magazine
The subsidence being seen in Joshimath did not just happen overnight. We have known for a long time that the town is vulnerable to subsidence. In 1976, a report by the committee led by MC Mishra, then commissioner of Garhwal division of undivided Uttar Pradesh, noted that Joshimath was sitting on an ancient glacial deposit (the report calls it an old landslide zone).
The report had warned that the town could “sink” if development continued unchecked and recommended minimum disturbance. Had we measured the carrying capacity of the region and monitored the subsidence, we could have identified the factors responsible for the situation and averted the disaster.
Studies, including the recent space satellite images shared by Indian Space Research Organisation (ISRO), have found that the town has been sinking for a while. The January 11, 2023 report by ISRO said the ground surface in Joshimath recorded a subsidence of around 9 cm between April and November 2022 before rapidly dropping roughly 5 cm in merely 12 days in December-January.
Read more: Sinking town: Probe NTPC project, say experts as subsidence creates panic in Joshimath
However, the report was pulled down later as the National Disaster Management Authority on January 13 imposed a “gag order” on scientists from government institutes, preventing them from interacting with the media or sharing data on social media on matters related to the Joshimath incident. Such restrictions on information flow are self-defeating. So, from a scientific point of view, we missed the chance to understand the crisis at Joshimath.
There are currently many speculations about what could have happened. Experts are being deputed to undertake detailed studies to understand the events that led to the disaster.
On January 10, 2023, Jitendra Singh, Union Minister of State for Science and Technology and of Earth Sciences, said the government would install numerous micro-seismic observation systems at Joshimath to investigate whether small earthquakes (with a magnitude of less than 3) and tremors triggered the subsidence.
I do not think earthquakes caused the current disaster. Large earthquakes, which can contribute to land subsidence, happen when two tectonic plates on either side of the fault line go up or down with respect to each other. There have been no reports of such surface deformation at Joshimath.
Micro-earthquake activities and slow movement along faults also contribute to some amount of subsidence in the long run. Only sensors can pick up such activities. In such cases, areas adjoining Joshimath should also have some fault-related surface-level changes. But so far, subsidence is restricted to the town area.
ISRO’s findings on long-term slow subsidence also rule out the possibility of any micro-earthquake being the causative factor.
Of course, monitoring seismic activities in the Himalayas, including Joshimath, is essential. But a different kind of mechanism appears to be at play here. Some experts from the government-run institutes have stated that poor drainage due to population pressure has impacted the surface run-off disposal and the consequent pressure exerted by the percolating water, as what would be expected in a landslide, could cause fissuring and sinking.
Read more: Joshimath won’t be saved unless NTPC’s project is shelved: Expert’s dire warning
Across the world, groundwater depletion is recognised as a cause of subsidence. In Joshimath, tunnelling and other engineering projects could have damaged water-bearing aquifers, leading to leakage of massive amounts of water from the inter-bedded clays and silts within the glacially-deposited sediments on which the town is built. This would reduce the pore pressure, causing sediment shrinkage and land subsidence.
The Himalayas are home to many rivers, steep slopes and forests. The kind of infrastructure built in the plains cannot be built here. We must assess whether an area is suitable for construction before setting up infrastructure.
Building of roads and freeways must be sustainable and not lead to more landslides. The region has seen many disasters, and most of them are directly related to massive engineering projects planned in the area. Such projects impact the environment and destabilise the slopes. We must learn from earlier mishaps, accidents and disasters, monitor the region and devise plans to reduce human impact.
In 2021, some 509,503 people participated in the Chardham Yatra. The government is deploying marketing strategies to expand roads for pilgrim tourism; millions more will visit the region if high-speed railway and motor traffic is allowed. It will not be easy to regulate them.
At the same time, the Himalayan region is an active seismic zone. Damaging quakes could strike the region in the future.
An implementation plan that considers the carrying capacity of the terrain is the need of the hour, as is a proper land zonation and land utilisation strategy. We need to strictly implement these strategies and also listen to people living in this region for centuries.
The government argues that infrastructural development will increase employment. But the impacts seen now are leading to the opposite; people are losing livelihoods and their homes. The best course of action is to suspend all current massive infrastructural activities in the Himalayas, until a proper impact assessment is made and whetted by independent experts.
(As told to Rohini Krishnamurthy)
Stop all hydroelectric projects in Himalayan region to avoid a Joshimath repeat: Experts
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