KOCHI: What caused the landslide at Joshimath in Uttarakhand towards the fag end of 2022 and early 2023?
The answers to this question were unlocked by two geophysicists from the Space Application Centre-Indian Space Research Organisation (SAC-ISRO) and the Cochin University of Science and Technology (Cusat). The resultant paper that the duo has presented based on their extensive studies on the subject got international recognition when it was published in the May edition of the Geophysical Research Letters by the American Geophysical Union.
The research study, which was a collaborative work led by Dr Sreejith K M of SAC ISRO and Dr Sunil P S of the Department of Marine Geology and Geophysics, Cusat, found an alarming increase in the velocity of landslides in the Himalayan region.
According to Dr Sunil, during the reserach, the team used the Interferometric Synthetic Aperture Radar (a radar technique used in geodesy and remote sensing), Global Positioning System (GPS) and rainfall measurements to understand the geometry of the motion of the Joshimath landslide.
During the research, the geophysicists found that the Himalayan landslides occurred due to tectonic, hydrological and human activities.
"The trigger for our research was the catastrophic landslides that shook Joshimath, a densely populated Himalaya town during December 2022 and January 2023. Around 700 buildings got damaged," said Dr Sunil.
Explaining more about the research and the landslide phenomenon, Dr Sunil said, "While the low amplitude annual landslide motions are modulated by seasonal precipitation, acceleration phases are triggered by extreme rain events. Our analysis revealed episodes of cascading motions triggered by extreme rain events resulting in an overall increase in landslide velocity from 22 mm per year during 2004-2010 to 325 mm per year during 2022-23."
The researchers estimated the landslide depth and hydraulic diffusivity using a 1-D pore-water diffusion model (in this model, diffusion is assumed to take place in the liquid-filled pores).
"Our study reveals the importance of systematic monitoring of ground deformation and weather parameters for landslide hazard mitigation," Dr. Sunil added.
The study also found another active landslide 6 km southwest of Joshimath town that has been moving at a speed of approximately 75 mm per year since mid-2018.
