ABSTRACT
Frihy, O.E. and Stanley, J.-D., 0000. Suitable subsea sand-rich borrow areas to replenish eroded beaches of Egypt’s Nile Delta.
This study focuses on five potential borrow areas of high-quality sands that are identified and delineated on the inner and middle Nile Delta continental shelf. The areas will undergo subsequent detailed geotechnical exploration for possible sand sources suitable to nourish now-eroding beaches and inner shelf areas off northern Egypt. Six areas herein are identified as Ero 1 to Ero 6 from west to east. Location and mapping of these proposed borrow areas are based on integration of textural analysis of offshore core sections and historic borehole soil logs, mapping the late Pleistocene to Holocene stratigraphic sequences of the Nile Delta continental shelf (to ∼50 m thickness) and defining grain-size distributions and dynamics of seabed surficial sediments. The explored sand sources will be used to nourish Nile Delta beaches experiencing increased rates of down-drift erosion resulting from effects of constructed shore-perpendicular structures (jetties and groins), despite such features initially succeeding in reducing previous long-term chronic shore recessions after damming the Nile River by the Aswan High Dam in 1965. Only two subsurface sedimentary units are identified in examined borings on the shelf as potential resource sands that represent basal transgressive and coastal accretion sand ridges. These were previously documented in late Pleistocene and Holocene sequences recovered on the Nile Delta margin. Compatibility analysis indicate that these resource sands (medium-sized, moderately well sorted sands) are suitable to nourish existing eroding delta’s beaches, which comprise fine-sized, moderately well sorted sands. The results of this study facilitate the possibility of taking the next GO decision that confirms the probability of the presence, or not, of beach-quality sand suitable for replenishment of Nile Delta shores and adapting them to future relative sea-level rise, delta margin subsidence, and storm-induced sea flooding.
