Uttarakhand’s holy town of Joshimath started ‘sinking’ way back in 1976: Here’s why

Residents of the holy town of Joshimath in Uttarakhand have been concerned after spotting cracks in the town's buildings and streets, which they have described as the town "gradually sinking". Due to earth subsidence that caused 561 homes in Joshimath to develop cracks, the Uttarakhand government prohibited development work in the area on January 5 in response to protests from the terrified inhabitants. Let’s find out the science behind the Joshimath crisis.

Construction

Experts have spoken of the possibility of ground subsidence in the area more than ten years prior. This rapid and extensive dewatering of the stratum. The fact that the town is sinking is not shocking because no corrective actions were taken.

Several new multi-story structures are said to have sprouted up in and around Joshimath town in the last ten years or so, according to locals. Subsidence recently caused one of these buildings to tilt. Despite being well aware of the geological risk of the area, hydroelectric schemes have been approved near Joshimath and Tapovan, including the Vishnugad HE Project.

Also Read: Joshimath crisis: ‘Vertical sinking’ of sacred town in Uttarakhand displaces 38 families

Joshimath's problems with slope instability have gotten worse as a result of unplanned construction that didn't take bearing capacity into account, according to a survey report from the Uttarakhand State Disaster Management Authority (USDMA) from August 2022. Several additional buildings could be developed in the landslide-prone area by building retaining walls. As a result, there is now increased strain on the weak slope.

The Border Roads Organization (BRO) is employing large machinery to construct a Helang bypass, which will cut the journey to the Badrinath shrine by around 30 kilometres. According to experts, this development beneath the tectonic activity may cause more landslides. The Mishra Commission had cautioned against substantial building in the vicinity of Joshimath in its 1976 report.

Geography

A report from the 1976 Mishra Commission noted the first case of sinking in Joshimath, which is situated in a region vulnerable to landslides. The town is located on the middle slopes of a hill that is bordered on the west and east by the Karmanasa and Dhaknala streams and on the south and north by the Dhauliganga and Alaknanda rivers.

Dhaknala, Karmanasa, Patalganga, Belakuchi and Garurganga are just a few of the streams that have their beginnings in the Central Himalayan region near Kunwari Pass. While the others empty into the Alaknanda, the first is a tributary of the Dhauliganga. Due to the flash floods that followed their blockage by landslides, these streams are infamous for the destruction they have previously inflicted.

The most recent satellite data shows that mountain streams have altered their courses and extended their channels, adding to an already vulnerable belt's slope instability. This is evidence of the influence of significant rainfall events.

Joshimath is extremely prone to sinking due to tectonic activity because it is on a fault line and close to two other ones. A geological fault line called the Vaikrita Thrust (VT) almost touches Joshimath. Additionally, the Main Central Thrust (MCT) and Pandukeshwar Thrust (PT), two major geological faults, are relatively near the town. Joshimath Village is placed within the effect zone of any tectonic activity on MCT as it passes beneath Helang, a small town to the south of Joshimath Town, and juxtaposes with the rocks of the Garhwal Group.

Drainage

A likely cause of sinking, increased ground seepage of water from the surface was highlighted by experts and the USDMA. Anthropogenic surface-level activities have obstructed natural water drainage systems, pushing water to seek out alternate drainage pathways.

Also, there is no sewage or wastewater disposal system in the town of Joshimath. The seepage weakens the overburdened soil's shear strength. This may be seen in the area surrounding Sunil Village in Joshimath, where the water lines have bent out of shape due to subsidence.