Eastern Joshimath records maximum subsidence of 10cm per yr, says study STREAM BURST NOT LINKED TO CONSTRUCTION OF TUNNEL: GOVT

DEHRADUN: A fresh analysis of satellite imagery of Joshimath between 2018 and 2022 showed that the eastern part of the holy town witnessed maximum subsidence with an average displacement of around 10 cm per year, reiterating what the Indian Space Research Organisation (ISRO) said.

The analysis, by remote sensing and landslide experts of Centre National de la Recherche Scientifique (CNRS or National Centre for Scientific Research, which is the French state research organisation and largest fundamental science agency in Europe), Ecole et Observatoire des Sciences de la Terre Strasbourg (School and Observatory for Earth Sciences, an institution under the supervisory authority of the University of Strasbourg France and CNRS) and Aristotle University of Thessaloniki, Greece, was accessed by HT on Thursday.

The study pointed to specific areas in Joshimath which witnessed maximum sliding (or subsidence) in the last four years. According to the study, the eastern part of the town, designated as unit A, recorded maximum sliding of 10 cm per year followed by the western side, designated as B, with annual displacement of 3 cm.

The sliding in lower part of the town, shown as unit C, had accelerated since January 2021, the study showed. The upper part of the town, marked as D, showed the least displacement of 2 cm per year, it added. “It appears that two zones (eastern and western parts of Joshimath designated as A and B in the satellite image) have been continuously moving in the past four years (2018-2022) on the downhill part of the slope. The surface displacement rates are higher in the eastern part of the slope (unit A) with a value exceeding 10 cm per year for the period 2018 to 2022,” the study said.

Following an acceleration in subsidence in early January, the state has been forced to relocate people, and embark on a planned demolition of the worst affected commercial structures.

The analysis said that subsidence has accelerated in the eastern, western and lower parts of Joshimath town since December 22 but did not provide data on how much the town has sunk since then.

The findings are consistent with the latest analysis of satellite images of the area by ISRO and recent field observations.

According to two reports of the ISRO’s affiliates, National Remote Sensing Centre and the Indian Institute of Remote Sensing, land subsidence in Joshimath increased rapidly, especially in the 13-day period between December 27 and January 8 when the town witnessed a subsidence of 5.4 cm.

YP Sundriyal, a geologist from HNB Garhwal University, Srinagar, said the fresh analysis confirmed what locals have been saying since last year. “The subsidence rates increased in December and in the first week of January, which is consistent with the cracks in 849 houses and ground fissures reported in Joshimath. The government should use this data for long-term planning for Joshimath and evacuate people from the area at the earliest.”

Atul Sati, convenor of Joshimath Bachao Sangharsh Samiti, said the new analysis by international experts made it clear how acute the Joshimath crisis is.

DEHRADUN: The Uttarakhand government on Thursday said that the underground water stream that burst beneath the Joshimath town, possibly accelerating the subsidence there, was not on account of the construction of a tunnel by NTPC for a hydroelectric project as claimed by affected residents.

Uttarakhand disaster management secretary Ranjit Kumar Sinha said a preliminary report of the National Institute of Hydrology (NIH), Roorkee, found that the water outflow in Joshimath and from the tunnel of the NTPC project are different. “The situation will be clear after the reports of other central agencies and the final report of NIH comes,” he told reporters.

Residents said the government has given a clean chit to NTPC without waiting for the final report.

NTPC is building the Tapovan hydel project, for which a tunnel is being dug below the Joshimath hills, with residents saying that blasting in the tunnel caused an underground aquifer or stream to burst, exacerbating subsidence in the holy town. Sinha said the discharge of water from the stream in Joshimath, which was 540 LPM (litres per minute) on January 6, has declined to 150 LPM,

Responding to his comments, Atul Sati, convenor of Joshimath Bachao Sangharsh Samiti (JBSS), said: “It is clear that the government is giving a clean chit to NTPC before the final report of NIH and other institutions is to come. If they have nothing to hide, then they should make NIH’s preliminary report public as this is a matter of life and death for us. If the report is made public, the affected people here can make their own decision.” NTPC has consistently refuted the allegation against its project and said no blasts were conducted for the underground tunnel. It described the subsidence as a “natural” process in the Himalayas.”