Monitoring recent land subsidence in the Nile Delta of Egypt using Sentinel-1 InSAR time series

The sinking of the Nile Delta presents a challenge to the Egyptian government because of its projected adverse economic, environmental and social impacts on the country. Previous studies have indicated that the Nile Delta is vulnerable to high rates of land subsidence, sea level rise, inundation, beach erosion, and salinization. In this study, we investigate present rates and patterns of ground deformation in Nile Delta using Sentinel-1 data and Persistent Scatterer Interferometry (PSI) techniques. The subsidence rates for the Nile Delta were estimated from a stack of 191 Sentinel-1 ascending scenes spanning a period of 5 years (2014 to 2019). The preliminary results include the following. (1) High rates of subsidence over cities proximal to the two main active branches (Damietta and Rosetta) of the Nile Delta, in agreement with the earlier ENVISAT-based InSAR observations. (2) The highest rates of subsidence (12-24 mm/year) were observed over the city of Damiat close to the Mediterranean coastline. (3) Areas of localized moderate subsidence were observed over the recent urban developments. (4) High rates of subsidence (up to 10 mm/yr) were detected over an oil field (10 km²) in the Western Desert of Egypt. Future efforts will focus on (1) analyzing the descending set (139 scenes) of Sentinel-1 acquisitions and extracting vertical component of deformation by combining descending and ascending displacement measurements, (2) calibrating InSAR-based deformation estimates with GPS time series, (3) comparing the results with earlier ENVISAT-based InSAR observations, and (4) investigating the factors controlling the observed deformation using geophysical and hydrological datasets.