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Abstract

Joshimath is an Indian Himalayan town built on a paleo landslide and fragile mountain slope of a landslide-prone region. By the end of 2022, local people identified numerous cracks in the buildings and grounds of Joshimath. The local administration ordered to demolish the unsafe structures to minimize socioeconomic losses, resulting in conflict between people and the administration. The leading cause of these crack developments or land subsidence are the construction activity of NTPC’s Tapovan-Vishnugad hydro project, rapid urbanization, and population overgrowth. However, the local geological conditions, including lithology and thrust zone, control the magnitude of land subsidence. Microwave Remote sensing, mainly the Persistent Scatterer Interferometry Synthetic Aperture Radar (PSInSAR) technique, has emerged as a promising tool for monitoring land subsidence with millimetre precision. Hence, in this study, we have used 32 Sentinel-1 SLC images acquired from January 2022 to January 2023 along ascending orbit to track land subsidence over the Joshimath area. The StaMPS algorithm processed the InSAR images by considering 0.4 as the amplitude dispersion threshold, 3 patches in range and 2 patches in azimuth. The results revealed a significant land displacement rate of -0.5mm/year to -65mm/year. High displacement rates are observed in various locations on debris of paleo landslide. Similar subsidence has been reported by local news channels at various other locations in Himalayas. Further, work can be carried out to estimate the rates of deformation at other locations as well, such as Shimla, Dharamshala, Theog, Kufri, Almora, Nainital, Mussoorie, and other mountainous regions around the globe.