Ground subsidence monitoring with SAR interferometry techniques in the rural area of Al Wagan, UAE

Abstract

In this work, we investigate the past and present land deformation in Al Wagan area in the United Arab Emirates. The area is primarily an agricultural region where dependence on groundwater is documented. Such a reliance on ground water resources in a region which is characterized by very low precipitation can lead to significant land subsidence as was observed in this study which identified fast and localized deformation trends. The quantification of ground deformations of large magnitude and small amplitude in this area with SAR Interferometry is a challenging task using moderate resolution data due to the incoherent surface background. Even though SAR acquisitions were sparse over this region, the available ENVISAT, ALOS and Sentinel-1A imagery was analysed with differential interferometry and the Small Baseline Subset technique in order to provide estimates about the evolution of the deformation pattern in a limited area. A clear evidence of subsidence phenomena has been identified in the study area. During the period 2003–2010 the subsidence was estimated to reach 18 cm/year as observed in the DInSAR processing results of data from ENVISAT and ALOS Satellites. However it appears to be slightly more stable during the recent past (Dec/2016–March/2018) as observed in the results with recent Sentinel-1 data where a maximum localized subsidence in the order of 10 cm was estimated. The depletion of the aquifer resources which is confirmed from groundwater level data is speculated to be the most probable cause.