Quantitative Assessment and Driving Factors of Land Subsidence in Northern Hamadan Province, Iran

Land subsidence is one of the most serious threats to many plains in arid and semi-arid regions. The northern plains of Hamadan Province in western Iran are among the at-risk areas. Given the serious consequences of subsidence, this study aims to assess the current state of land subsidence in the northern plains of Hamadan and analyze the contributing factors. The research utilizes Sentinel-1 radar imagery, statistical data from regional piezometric wells, and a 1:100,000-scale geological map, and various digital data layers as the primary data sources. Key tools employed in the study include ArcGIS, GMT, and Google Earth Engine. First, land subsidence in the study area was mapped using the Small Baseline Subset (SBAS) time-series method. This was followed by an analysis of the relationship between observed subsidence and environmental factors. The results indicate that, between 2018 and 2022, subsidence in the study area ranged from 44 to 289 millimeters, with the highest values observed in the region between the cities of Famenin and Kabudarahang. The findings indicate that, due to alluvial lithology and the absence of geomorphological barriers, a significant portion of the study area consists of agricultural land. This has led to significant declines in groundwater levels, with several wells in the region recording drops exceeding 2 meters per year. A strong positive correlation (r = 0.57) was identified between the subsidence layer and groundwater level decline, suggesting that groundwater depletion is the primary driver of land subsidence in thae area.