Assessing Land Deformation and Sea Encroachment in the Nile Delta: A Radar Interferometric and Inundation Modeling Approach

Persistent scatterer interferometric analyses were conducted on a stack of 84 Environmental Satellite's Advanced Synthetic Aperture Radar scenes spanning 7years (2004 to 2010) over the entire Nile Delta of Egypt and surroundings (area: 40,416km(2)) to monitor the ongoing spatial and temporal land deformation, identify the factors controlling the deformation, and model the interplay between sea level rise and land subsidence to identify areas and populations threatened by sea encroachment by the end of the 21st century. Findings include the following: (1) general patterns of subsidence (average rate: -2.4mm/year) in the northern delta, near-steady to slight subsidence in the southern delta (average rate: 0.4mm/year), separated by a previously mapped flexure zone (minimum width: 20-40km) undergoing uplift (average rate: 2.5mm/year); (2) high subsidence rates (up to -8.9mm/year) over the north central and northeastern delta (area: similar to 4,815km(2)), possibly due to compaction of recent (<3,500years old), thick (>5m) silt and clay-rich Holocene sediments; (3) high subsidence rates (up to -9.7mm/year) in areas where the highest groundwater extraction rates were reported in southern delta (Menoufia governorate) and in reclaimed desert land in the western delta (Beheira governorate); (4) high subsidence rates (up to -9.7mm/year) over onshore gas fields, notably the Abu Madi gas field, where high gas extraction rates have been recorded; and (5) using extracted deformation rates, high-resolution TanDEM-X digital elevation model, a eustatic sea level rise of 0.44m, and applying a bathtub inundation model, an estimated 2,660km(2) in northern delta will be inundated by year 2100.