In January 2023, over 800 houses developed cracks overnight in Joshimath, a Himalayan town in Uttarakhand’s Chamoli district, forcing terrified families to evacuate the hilly terrain. The ground beneath Joshimath continues to give way. An analysis of the subsidence shows that between December 2022 and December 2024, parts of Joshimath sunk by more than 30 cm. The worst-affected areas include densely packed human settlements and two national highways, with various stretches inside the municipality collapsing at alarming rates—anywhere from 5 cm to over 30 cm in just two years. Situated in the most earthquake-prone zone in the Himalayas, Joshimath stands on ancient landslide debris—a foundation prone to subsidence—yet unchecked urban expansion continues. In the past 17 years, the built-up area has nearly doubled, pushing the town towards further catastrophe.
The ground subsidence in Joshimath has been assessed using the Small Baseline Subset (SBAS) SAR technique, which employs Synthetic Aperture Radar (SAR) to monitor ground displacement with high precision. The analysis spans two distinct periods: December 2022-December 2023 and December 2023-December 2024.
The results indicate displacement ranging from -20.7 cm to +17.4 cm in 2022-2023 and -24.5 cm to +22.9 cm in 2023-2024. To improve visual interpretation, displacement data across the valley have been aggregated to estimate the total approximate subsidence over the two-year period.The study relies on data from multiple sources, including Copernicus Sentinel-1, Google Building Footprint, OpenStreetMap, SRTM, and the research paper “Analyzing Joshimath’s Sinking: Causes, Consequences, and Future Prospects with Remote Sensing Techniques”, published in Nature on May 13, 2024.
This was first published in the 1-15 April, 2025 print edition of Down To Earth