Separate studies conducted by eight premier Institutions of India to know the cause of land subsidence in Joshimath town of Uttarakhand attributed to the seismic activities, construction loopholes, population pressure, poor drainage system among others as ‘likely’ reason for the sinking of the Himalayan town. With every study conducted with a different approach, these reports largely recreated the sensitivity of the area but nothing concrete has come out on what exactly went wrong last January, say experts.
The eight institutions — the Wadia Institute of Himalayan Geology (WIHG), the National Geophysical Research Institute (NGRI), the National Institute of Hydrology (NIH), the Indian Institute Of Technology (IIT-Roorkee), the Indian Institute of Remote Sensing (IIRS), the Geological Survey of India (GSI), the Central Ground Water Board (CGWB) and the Central Building Research Institute (CBRI) — were given the mandate to identify the causes of land subsidence by the government. The reports of these institutions were submitted earlier this year but they were made public only after the Uttarakhand High Court last week questioned the State for hiding them.
In its report, the CBRI stated that the Joshimath town has 44%, 42%, 14% of masonry, RCC and other (traditional, hybrid) construction typologies among which 99% are non-engineered — means they are not complying with the National Building Code of India 2016 provisions.
“Joshimath town is situated on Vaikrita groups of rocks overlain by morainic deposits which are composed of irregular boulders and clay of varying thicknesses. Such deposits are less cohesive and susceptible to slow subsidence and landslide subsidence,” the CBRI said.
It added that there is a history of creeping and occasional subsidence in the region and what happened in December-2022-January 2023 was another such event. It further suggested that there is a need for reviewing the principles of town planning for development of towns in hilly regions.
Roorkee based-NIH, in its report, said that various spring, drainage network, areas of subsidence maps infer that land subsidence and subsurface water in the Joshimath area might have some connections.
Clean chit to NTPC
“The isotopic and water quality signature of the samples taken from NTPC sites differs from the JP site as well as drains and springs in the nearby area of Joshimath. The bacteriological analysis also suggested that the gush water is fresh water and not contaminated by the local drains,” the report suggested and hence giving a clean chit to the NTPC whose construction activities were being dubbed as one of the biggest reason for land subsidence in Joshimath by local activists.
The institution hence recommended the safe disposal of the water coming from the upper reaches and waste of town should be the top priority.
The WIHG mentioned earthquakes as reason for slow and gradual land subsidence in the area and used the opportunity to draw the government’s attention to its long-pending demand of LiDar sensors.
“Since Uttarakhand is a mountain State, and often faces mountain disasters, it is of utmost importance that LiDAR topographic mapping is done for the State. Planning of management and mitigation is convenient if bare-ground topography and the surface models are available to planners and decision makers,” the WIGH stated.
Complex mixture
IIT-Roorkee suggested that the overall soil fabric of Joshimath is found to be a complex mixture of boulders, gravels and soil, the internal erosion in such soils causes the instability of the whole fabric and results in the readjustment of the boulders, leading to subsidence.
“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/wastewater discharge from household and hotels. Though subsidence is continuous phenomenon, it can be minimised by controlling infiltration of water, which helps in minimising the internal erosion,” the report of IIT-R said.
Analysing by Small BAseline Subset (SBAS) Interferometry SAR Technique, the ISRO stated that the subsidence in Joshimath region may be due to toe-cutting phenomenon, slope instability as a result of seepage of local drainage water in the soil, terrain and edaphic characteristics, loose and unconsolidated moraine materials of the slope (due to old landslide) and flash flood events in and around the area in the recent past. This has resulted in development of cracks in the ground as well as houses in Joshimath town.
Mallika Bhanot, an environment activist in Uttarakhand, said that in 2012 after the Ukhimath disaster, there was a clear recommendation by the State Disaster Management department to completely stop blasting in the vicinity of Joshimath. The same report had also asked to regulate the infrastructure development activities in this area as well.
“Even after recommendations that arised from a disaster, why was the NTPC project allowed to continue in this area and why was chardham road widening project allowed in its vicinity as both needed blasting. I also ask why was there no regulation on the tourists’ inflow and a decade later when we witnessed another disaster, the policymakers and unfortunately even the scientific institutions conveniently blame it on the nature and inherent vulnerability of the area,” she said.
Geologist Navin Juyal termed the reports of the eight institutions ‘old wine in a new bottle’.
“These reports clearly said all that had been said 46 years ago in the M.C. Mishra Committee report,” said Mr. Juyal.
