SBAS-InSAR/GNSS Surface Deformation Assessment in Arid Environments of Najran, Saudi Arabia

Multiple surface fissures were reported over the last few years within the Najran valley, southern Saudi Arabia. The earth fissures have been observed mainly in the vicinity of agricultural territories. This study maps the surface deformation of Najran valley using geodetic data and investigates the underlying mechanisms. Indeed, we use Interferometric Synthetic Aperture Radar (InSAR) technique with standard Sentinel-1 Geocoded UNWrapped interferogram (GUNW) products acquisition from 2016 to 2022 and processed by Advanced Rapid Imaging and Analysis (ARIA) project using InSAR Scientific Computing Environment (ISCE). We generate displacement time series using the Miami INsar Time series software in Python language (MintPy). The result shows a rate of subsidence within the Najran valley ranging between 0.2 and 0.6 cm/yr. We processed the Najran GNSS station with time series extended from 2017 to 2022 to validate the observed displacement field. We analyze groundwater variation and soil properties to interpret the results. This assessment verifies that the potential drivers of subsidence might be due to an excessive withdrawal of groundwater, with the potential contribution of other factors related to the sequence of drought and moisture in the soil layer. The presence of a fine-grained layer of soil (clay) suggests a potential impact on the observed deformation. The observed signal and potential underlying mechanism represent one of the classical problems in arid regions worldwide, our investigation is crucial to improve the environmental assessment of Najran valley, which may mitigate any potential future hazards.