Ground Deformation Monitoring in the UAE

  • Nikolaos Liosis

Student thesis: Doctoral Thesis

Abstract

In this thesis, the past and present ground deformations in the east Abu Dhabi Emirate and the city of Abu Dhabi were investigated. The former area is a mainly agricultural region where dependence on groundwater is documented, while the expansion of Abu Dhabi city towards the inland of the UAE has recently faced several engineering problems due to subsurface cavities. For this purpose, the groundwater-related displacement phenomena as well as those caused by karstic features were assessed and monitored by means of SAR Interferometry and multi-temporal interferometric techniques, such as SBAS and PSI, in order to mitigate the strong atmospheric effects. Despite the low coherence of the sand dune background that covers most of the study areas and the sparsity of known stable points to be used as reference, the use of ENVISAT, ALOS and Sentinel-1 data revealed the existence of several subsidence and uplift patterns in the rural areas that were not previously known, while their relation to the groundwater variations was also examined. The subsidence rates appeared to have reached 18 mm/year in the area of Al Wagan, but the trends appear to be decelerating in many occasions. The results were also validated with GPS measurements. The study of the hydrogeological setting in the area of Al Ain indicated the existence of a low conductivity zone along the groundwater flow direction, which suggested that one of the causes of the ground deformations, apart from the high irrigation demands, is the low lateral recharge in the agricultural regions. In order to further map the effects of the groundwater table variations, the changes in the vegetation cover and their trends were mapped with the use of optical sensors, such as Landsat and MODIS. It was found that the trends of the Normalized Differenced Vegetation Index (NDVI) and the land use changes also exhibited a strong relation with the groundwater. The PSI and SBAS techniques were also able to detect the localized cavity-related subsidence in the city of Abu Dhabi with Sentinel-1 data, which were validated with damage assessment surveys in buildings and other infrastructure.
Date of AwardJul 2018
Original languageAmerican English
SupervisorPrashanth Marpu (Supervisor)

Keywords

  • DInSAR
  • SBAS
  • groundwater
  • subsidence
  • UAE.

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