Investigation of the Physical Hazards of Land Subsidence in the Varamin Plain

Abstract

Land subsidence is one of the major environmental and geological challenges in urban and agricultural areas of Iran, including Varamin County. This phenomenon leads to the formation of cracks and deep depressions and creates various hazards such as disruption of urban infrastructure and agricultural areas. The city of Varamin is located on the relatively vast and flat Varamin Plain, which, due to excessive extraction of groundwater resources and the thickness of alluvial sediments, is highly exposed to this phenomenon. The data used in this study include Sentinel-1 images from the period October 8, 2014, to March 25, 2024, extracted from the Subsidence Portal. The remaining data were obtained through field surveys of the evidence and effects of subsidence, and their geographic locations were recorded using GPS, ground photography, and the spatial matching of the GPS points with Google Earth. Interferograms and coherence data were produced using the LiCSAR system based on the GMTSAR software and interferometry methods. The interferograms were processed within the overlapping frames defined in the COMET-LiCS system. To correct the atmospheric model, the GACOS tool and InSAR data were used to effectively eliminate atmospheric (tropospheric) noise. In order to determine a transverse profile of the subsidence in the Varamin area, the point at 35°33'8.52" N latitude and 51°41'2.13" E longitude, with an elevation of 1285.97 meters above sea level, was selected. The results obtained from the land subsidence data in Varamin County showed that the average annual subsidence during the period 2014–2024 was 68.1 cm. The subsidence zoning map indicates that the phenomenon is occurring with non-uniform distribution and varying intensities, with greater subsidence observed in the central regions of Varamin—likely due to human activities and excessive groundwater extraction. The maximum recorded subsidence in the Varamin Plain reached 140 cm. The average annual subsidence over the statistical period is 68.1 cm, increasing from no measurable subsidence in 2014 to 169 cm in 2023 and 38.7 cm in 2024. This indicates that land subsidence in Varamin County, although initially a seasonal hazard occurring mainly during dry periods and partially compensated during wet seasons, has since 2019 (1398 SY) evolved into a persistent crisis. Field evidence of subsidence also reveals the vulnerability of human structures, especially residential buildings, with some areas experiencing such damage that residents have been forced to abandon their homes.