The Indian Himalayan town of Joshimath, which witnessed an unprecedented and unexplained land subsidence phenomenon, seems to have sunk “vertically by over 3 feet and moved by 1.4 feet”, a report by the National Geophysical Research Institute (NGRI) has stated.

The NGRI is one of the eight institutions mandated by the Uttarakhand High Court to ascertain the causes of land subsidence and suggest remedial measures.

The report, which was allegedly kept secret by the state government, was made public recently on the order of the court.

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The report mentions that loose sediments, population pressure, construction of multi-storey buildings and the absence of a system for proper disposal of water coming from the upper reaches caused the Joshimath land to subside significantly.

According to its 43-page report, the middle and western side of the town saw land sinking, though isolated incidents were also observed in the whole of Joshimath town.

“Maximum horizontal displacement along the fissures was observed in Sunil, Manohar Bagh and Singhdhar with displacement as high as 45cm (1.4ft). Vertical displacement (sinking) as high as 110-110cm (3.6ft) was witnessed in Singhdhar and Marwari,” the report said.

The report also pointed to “steep, air-filled fissures extensively developed and extending to a depth exceeding 100ft”.

Unplanned construction, overpopulation blamed 

Joshimath, a historical town, is said to be built on the debris of a landslide triggered by an earthquake, and is located in a tremor-prone zone. It frequently witnesses landslides, which have reportedly weakened the soil.

Experts and environmental activists have been blaming unplanned construction activities, hydropower projects and improper drainage systems for the land subsidence.

The Central Building Research Institute (CBRI), which was among the institutes tasked to look into land sinking issue, in its report found that out of 2,364 buildings in Joshimath, 20 per cent of houses are “unusable”, 42 per cent are under “further assessment”, 37 per cent are “usable”, and one per cent of them “need to be demolished”.

“There is a need for reviewing the principles of town planning for development of towns in hilly regions with rigorous stress on good construction typology, practices, material, regulatory mechanism, and awareness among the stakeholders based on geo-technical and geo-climatic condition,” the CBRI said in its recommendation.

The Geological Survey of India (GSI) said it is strongly advised to carry out ground-based terrestrial monitoring in different parts of Joshimath.

“The main reason for the subsidence appears to be internal erosion caused by the subsurface drainage, which may be due to infiltration of rainwater/melting of ice/waste water discharge from household and hotels. Though subsidence is a continuous phenomenon, it can be minimized by controlling infiltration of water, which helps in minimising internal erosion,” the IIT-Roorkee said in its report.

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