Spatial Analysis of Ground Subsidence using Radar Interferometry (Case Study: Central Plain of Ghaen City)

Land subsidence is one of the most important geomorphic hazards that has a slow motion but destructive effects in the long run. For the spatial analysis of the amount of displacement, the data on changes of the ground surface from Sentinel A1 for a period of 3 years (2017-2020) through the radar interferometric method and SNAP software were used. Field observations were also made to evaluate the research results. The results showed that the rate of land subsidence has increased from 2017 to 2020, from 2.6 cm in 2017 to 7.8 cm in 2020. Moreover, the groundwater hydrograph in the central plain of Ghaen has significantly decreased, so that the rate of water level drop in the plain level has been about 1.30 meters during 5 years (from 2014 to March 2020), i.e, about 26 cm per year. In addition, the analysis of spatial autocorrelation and Moran index (0.984) confirmed the clustering of subsidence event under the influence of water level changes in the study area. The correlation results also showed that there was a small correlation between the factor “changes in water level” and “land subsidence rate” (p = -0.138), which is an indirect relationship, i.e., the higher the groundwater abstraction (or the lower the water level), the higher the amount of subsidence. But due to the level of significance (sig = 0.585) this relationship is not significant.