NEW DELHI: The widening of roads and construction of new ones in the Himalayan state of Uttarakhand has been causing incalculable damage to its fragile ecology. It has increased the landslide event to a dangerous level — one roadblocking landslide per kilometre.
A new study highlights the vulnerability of the Himalayan road network to landslides. Climate change and increasing footfall of tourists on the popular pilgrimage routes would further exacerbate the landslide risk along NH-7, it warns.
The NH-7 is a key arterial road connecting remote villages to transport goods and people. Frequent landslides disrupt the socio -economic development of the region and with possibility of human fatalities.
The study said road construction and widening are destabilising the slopes, which get further deteriorated after heavy rainfall. Rainfall or snowmelt increases the run-off, causing heavy soil erosion and subsequently creates conducive conditions for landslides.
Researchers observed that around 300 landslides occurred during monsoon in a stretch of 250 km between Rishikesh and Joshimath in Uttarakhand in 2022. There was a 30% jump in landslides due to slope failure as they become unstable during intense rainfall.
The study was published in the Natural Hazard and Earth System Sciences. Its researchers are associated with IIT Roorkee, Germany-based University of Potsdam and University of Berlin.
According to the study, between 2017 and 2022, around 11,000 km of roads were built in the Indian Himalayan states connecting rural mountainous regions. It involved slope undercutting, blasting and poor construction, making road maintenance challenging. Based on an inventory of more than 300 landslides along the estimated 250 km long corridor following exceptionally high rainfall during September and October 2022, the study identifies the main controls on the spatial occurrence of mass-movement events.
Cutting mountains
It underlines that cutting into mountain sides to create wider pathways often creates unstable slopes that are prone to failure. Further, the rock blasting required during the road widening process can lead to the fracturing and weakening of rock masses, creating potential landslide-prone zones along the road corridors. Clearing trees and vegetation for road widening eliminates their stabilising influence on slopes, thereby increasing the landslide hazard. Widening of roads can alter natural drainage patterns and potentially redirect water flow to adjacent slopes, thus causing water saturation, erosion and instability to the slope. Finally, it leads to increased surface runoff during heavy rainfall or snowmelt, saturating the soil and making it more susceptible to landslides.
The study indicates that 30% of the recorded landslides are reactivated slope failures, which underline how slopes get unstable during periods of intense rainfall. Climate change projections indicate a trend toward an increase in summer monsoon rain by 4-25%.
It, however, endorses the proposed 125 km long broad-gauge railway between Rishikesh and Karnprayag, saying a reduction in road traffic may disrupt the cycle of increasing hazard and exposure.