Bio:
Dr. Shubham Awasthi specialises in Synthetic Aperture Radar (SAR) Remote Sensing and its applications. He earned his Ph.D. from the Indian Institute of Technology Roorkee, India, where he developed advanced SAR techniques for Earth observation. His research included Time-Series InSAR, SAR Tomography, SAR Polarimetry, backscatter modeling, hybrid polarimetry, and deep learning for SAR data. These approaches were applied to land subsidence monitoring, 3D urban reconstruction, snow parameter retrieval (e.g., snow wetness and density), urban feature extraction, and flood mapping using Sentinel-1 data. He completed his M.Tech. in Remote Sensing and GIS from the Indian Institute of Remote Sensing (ISRO), Dehradun, with a specialization in Satellite Image Analysis and Photogrammetry. His M.Tech. dissertation focused on snow parameter retrieval using bistatic TerraSAR-X/TanDEM-X datasets and hybrid polarimetry for PolInSAR-based snow depth and density estimation. Dr. Awasthi is currently a Postdoctoral Researcher at Virginia Tech, USA, working on large-area land subsidence monitoring due to groundwater withdrawal and crustal deformation.
Abstract:
The Himalayas are inherently vulnerable to natural hazards such as tectonic land deformation, earthquakes, landslides, and extreme climatic events. The land subsidence crisis in Joshimath, a town in the Indian Himalayas, has brought this fragility into sharp focus, with widespread ground movement causing extensive structural damage and posing serious threats to life and infrastructure. The time-series Synthetic Aperture Radar Interferometry (InSAR) based Persistent Scatterer InSAR (PSInSAR) approach was used to monitor land deformation in the Joshimath region using multi-temporal Sentinel-1 datasets. The results reveal significant line-of-sight (LOS) deformation velocities ranging from −89.33 mm/year (subsidence) to +94.46 mm/year (uplift) during the period 2022–2023. These findings are corroborated by feature-tracking analysis using high-resolution PlanetScope imagery, providing an additional layer of validation. Land deformation trends were also analyzed for earlier periods (2016–2017, 2018–2019, and 2020–2021), revealing that the most severe subsidence occurred in 2022–2023. The northwestern part of Joshimath, particularly around Singhdwar, exhibited the greatest subsidence, while the southern and southeastern zones showed both uplift and expansion. To better understand ground-level impacts, UAV surveys were conducted in critical zones such as Singhdhaar, Hotel Mountain View, Malari Hotel, and Manoharbagh, capturing fine-scale surface changes and structural damage. The study attributes the crisis primarily to unregulated anthropogenic activities, rapid infrastructural development, and inadequate drainage systems, which exacerbate the region’s natural vulnerabilities. The research calls for immediate action through integrated development policies, guided by remote sensing and ground-based observations, to ensure sustainable planning in ecologically fragile Himalayan regions.