SUBSIDENCE OF THE NILE DELTA, EGYPT: OPTIMIZING INTERFEROMETRIC SYNTHETIC APERTURE RADAR (INSAR) RESULTS OVER URBAN CENTERS IN VEGETATED REGIONS

Interferometric Synthetic Aperture Radar (InSAR) has become a popular remote sensing tool for measuring a variety of ground movements and deformation. Persistent Scatterers Interferometry (PSI) – a specific type of InSAR technique – works well in calculating ground displacements over a long period of time. Many variables directly affect PSI outputs, such as the spatial baseline, the temporal baseline, the Doppler centroid, the digital elevation model resolution, and atmospheric activity (i.e., precipitation) at the time of scene acquisition. An in-depth analysis of parameter values for the combination of single-look complex (SLC) images used in the PSI technique should be performed to yield optimized results and eliminate noise. The Nile Delta of Egypt is the study area of choice because it is highly populated, yet densely vegetated, and is therefore a complex amalgamation of regions of high-coherence and random scatter. The objective of this study is three-fold: (1) to examine the experimental process of SLC scene inclusion or elimination and the use of additional third-party datasets in order to optimize PSI outputs based on specified input parameters, (2) to calculate subsidence rates on city-scale areas of the Nile Delta, and (3) to investigate the factors controlling the subsidence in the study area. Findings include: optimum results (high coherence) were observed over cities, PSI calculations of tens of cities across the delta yielded subsidence rates as high 10 millimeters/year, progressively increasing subsidence rates were detected with decreasing distances from the shoreline, and many cities display a wide range of ground motion velocities which we relate to subsidence due to sediment compaction and anthropogenic factors.