Multi-temporal InSAR and Sentinel-1 for assessing land surface movement of Joshimath town, India

This study deals with the spatio-temporal measurement of land movement in Joshimath town using multi-temporal SBAS-InSAR technique. A network of 424 small-baseline interferograms was generated using 111 Sentinel-1 images acquired during May 2019-April 2023. Spatial distribution of line of sight displacement (LOSD) shows south-eastern Pekamarwadi, southern Gandhinagar and central Sunil wards are majorly affected; Manoharbagh, Singhdhar, and Lowerbazar moderately affected; northern Ravigram minor affected; and Parsari ward has no sign of land movement during investigation period. The observed negative values of mean LOS velocity and acceleration in southern Gandhinagar and central Sunil indicate these patchy areas are still susceptible and riskier for land stability. The SBAS-InSAR results were validated with CORS data during January 2022-March 2023. Trends show the gradual increase in LOSD from January to November 2022, rapid increase started from November 2022 and nearly ended mid January 2023, which indicates the initiation of movement stabilization. Accuracy assessment was performed in terms of Nash-Sutcliffe efficiency coefficient (NSE), R 2 , RMSE, and MAE, and the estimated values are 0.9896, 0.9495, 1.7534 cm, and 1.4028 cm, respectively. The analysis supports that CORS and SBAS-InSAR observed LOSD are in good agreement and reveals the true story of the land movement of Joshimath.