Scientists have discovered that vulnerability of the freeway stretch in Uttarakhand between Joshimath and Rishikesh to landslides is probably going to enhance, owing to continued vegetation removing and destabilising of slopes.

An common landslide density of 1.25 landslides per km was recorded by scientists for the 247-km-long stretch on NH-7 freeway.

The examine carried out a scientific survey of landslides and derived a statistical mannequin, aimed toward quantifying landslide susceptibility alongside the NH-7 at a excessive spatial decision, the findings mentioned.

Based on a list of greater than 300 landslides alongside the hall following exceptionally excessive rainfall in September and October 2022, the examine recognized the principle components governing the incidence of mass-movement occasions.

The findings of the examine have been introduced out in a preprint paper by scientists from University of Potsdam in Germany and Indian Institute of Technology in Roorkee.

“The highest density of landslides happens between Rishikesh and Srinagar inside lithozone 2 and between Pipalkoti and Joshimath in lithozone 1,” the examine mentioned.

“Lithozones encompass rocks of similar lithology, or composition. We did a regrouping of the lithologies from the geological map of Uttarakhand,” mentioned examine writer Jurgen Mey, Institute of Environmental Science and Geography on the University of Potsdam.

The excessive landslide density in lithozone 2 is probably going associated due to the pronounced fissility, or the capability to shear alongside the grain, and cleavage of the dominating shales and phyllites related to materials softening, percolation and weathering, inflicting a basic lower in rock energy, the examine mentioned.

“Yes, these rocks are susceptible to heavy rainfall. But many components of the Himalayas have related options, so it’s exhausting to keep away from such terrains. However, with correct stability measures, such slopes could be made safer,” said Reet Kamal Tiwari, assistant professor, Department of Civil Engineering at Indian Institute of Technology in Punjab’s Ropar.

Tectonic activity too contributes to a general decrease in rock strength by creating shear surfaces with low friction angles, the study said.

“Because the Himalayas are tectonically active, these rocks have been deformed and modified so that they feature a lot of discontinuities, along which they can fail more easily. Adding the steep slopes and the high intensity rainfall (trigger), landslides will be frequent,” mentioned Mey.

Road segments, the place the adjoining hill slopes parallel bedding, joints or foliation planes are significantly susceptible, the examine mentioned.

The examine discovered an intriguing spatial settlement between current constructions for highway widenings and landslide occurrences in the area below investigation.

The highway was widened by eradicating vegetation and excavating soil and rocks, probably creating unstable slopes, the examine mentioned.

“Land cowl change and local weather change are the dynamic components influencing landslide incidence, whereas, slope diploma and the soil are fixed components.

“We will see a rise in landslides in future, if the land use continues to change as per the present pattern. We want to analyse these developments and preserve them in entrance of us throughout city planning and different such actions,” mentioned Tiwari.

In fact, these disturbances have led to frequent landslides along the NH-7 previously as there have been previous studies also reporting about 300 landslides occurring along the road more than 10 years ago, the study said.

“Our data indicates that 20–40 per cent of the recorded landslides are reactivated slope failures which underscores that slopes are recurrently unstable during periods with intense rainfall,” the examine mentioned.

“We will see extra landslides in the long run in the Himalayan area if such heavy rainfall situations proceed,” said Tiwari.

During mapping, the scientists also noticed that some slopes were engineered during the last years with retaining walls, yet many of which also failed.

Damages and fatalities may become even more frequent in the future, the study said.

The entire Upper Ganga basin is susceptible to extreme rainfall events and climate change projections – although subject to high uncertainties – indicate a trend towards more frequent extreme events due to elevation-dependent warming and a likely increase of summer monsoon precipitation by 4-25 per cent, the study said.

It also said that exposure to landslides was likely to increase.

Road construction and increased traffic volumes attract more people, who will strive for new economic opportunities associated with roadside sites. These sites are often more susceptible to landslides as construction often implies vegetation removal and slope destabilization, the study said.

A reduction of traffic may disrupt the cycle of increasing hazard and exposure, the study said.

It concluded that the main controlling variables for landslides occurrence are slope angle, rainfall amount and lithology.

The Himalayan landscape presents a challenging environment for the construction and the maintenance of roads, even as close to 11,000 km of roads were built in the Indian Himalayan states, as attributed to media reports.

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