The land subsidence in Joshimath has increased rapidly with the Himalayan town sinking by 5.4 cm over 12 days from December 27 to January 8, the National Remote Sensing Centre (NRSC) has said in a report based on satellite images and prompted calls for the expedited shifting of the residents to safer locations.
The authorities on Thursday began the process of demolishing a subsidence-hit hotel as Uttarakhand chief minister Pushkar Singh Dhami cited growing scientific evidence about the sinking of land in parts of the town. Around 700 buildings in the town have developed cracks.
The report of NRSC, an Indian Space Research Organisation (ISRO) centre that manages data from aerial and satellite sources, said there was slow subsidence of 8.9 cm earlier over a period of seven months between April and November 2022.
“Between 27th December 2022 and 8th January 2023 (possibly on 2nd January 2022 as per eyewitness reports) a rapid subsidence event was triggered.”
The report said the subsidence zone is confined to Joshimath town’s central part around Narsingh Temple and resembles a generic landslide shape with a tapered top and fanned-out base. It added the crown of the subsidence was near Joshimath-Auli road at a height of 2180 metres. NRSC said the areal extent of subsidence has also increased.
Another report by the Indian Institute of Remote Sensing (IIRS) cited surface deformation observed through space-based radar interferometry and said there was a subsidence of up to 6.6 cm between July 2020 and March 2022
“Persistent Scatterer Interferometry (PSI) technique was used to estimate the land surface movement of Joshimath town for a period of July 2020 –March 2022…The results showed a significant subsidence rate in the Joshimath,” it said, referring to the remote sensing technique for measuring and monitoring displacements of the earth’s surface.
The reports concluded there has been 20.9 cm cumulatively subsidence since July 2020.
HNB Garhwal University geologist YP Sundriyal cited alarming subsidence data and said around 25% of Joshimath was rapidly sinking. Sundriyal said the data hints that the rate of subsidence may further speed up, especially if its rains. “Given the fresh data, the state government should expedite the shifting of the locals to safer locations at the earliest.”
Sundriyal said the first priority now should be to save the people and the town later
Environmentalist Hemant Dhyani, who is a member of the Supreme Court-appointed panel on the highway project to connect four Hindu shrines of Char Dham in Uttarakhand, said the fresh data shows subsidence in particular times intervals. “But in the absence of long-term data, we have no idea about the general rate of subsidence and whether it has been increasing over the years and at what rate.”
Dhyani echoed Sundriyal and said if subsidence is now rapidly increasing, the first thing government should do is to shift all residents to safer locations.
The reports echo what residents have been saying about the increase in subsidence this year.
Lakshmi Prasad, a resident, said the cracks in his house started appearing around seven months ago but the situation worsened on January 2 when they felt the ground was shaking as if an earthquake had hit.
RP Sati, another resident, said the cracks in the houses were reported first in Sunil Ward 14 months back and since then they have been getting wider. “…in the first week of January, cracks in houses deepened and big fissures started appearing in the ground.”
Rupesh Shah, a third resident, said NTPC has carried out continuous blasting to move a stuck tunnel boring machine. “The frequency of blasting increased in December, but on the night of January 2 and 3, the explosion was so strong that everybody in the neighbourhood felt it.”
The authorities on Thursday managed to get the consent of the owners of Hotel Malari Inn to demolish it after two days of protests. The hotel has been left tilting dangerously due to the land subsidence, which first surfaced in November.
Experts and locals have blamed the subsidence on damage to the underground water strata from NTPC’s tunneling work, unplanned development in the town, and the use of heavy machinery for the construction of the Helang bypass as part of the Char Dham road project.
Dhami stoked a row by arguing the sinking and cracks in buildings were a “natural disaster” not caused by anyone.
Experts have blamed projects such as the NTPC hydro power project in fragile geology despite warnings about their catastrophic consequences.