The sedimentological response of the Nile Littoral Cell to the Aswan Dam construction and other coastal anthropogenic alterations

The natural cycle of sediment transport along the Nile Littoral Cell was profoundly altered during the 20^th century and the present sediment balance along the continental shelf is a product of natural processes and anthropogenic intervention. A major control on the sediment budget of the Nile Littoral Cell (NLC) was the Aswan Dam construction as it terminated the transport of suspended sediments and nutrient into the Mediterranean. Furthermore, the growing agricultural land use, industrial activities and demographic growth along the coast altered the land cover and affected the sediment transport to the continental shelf. We present sedimentological evidence for the change. Sediment flux, grain size distribution, and carbonate content integrated with detailed ²¹⁰Pb dating from short cores and sediment traps at the distal part of the NLC reveal a change in the sedimentological regime. Drastic coarsening of the upper sediment cores dated to the last decades (see figure), and increase in the carbonate content is the main phenomena. The sedimentological change is smoothened when grain size distribution is measured only on the carbonate-free fraction. These results suggest that there is a reduction in the fine suspended Nile-driven silisiclastics that leads to the dominance of the local biogenic and authigenic fraction. The lead-210 dating was tested using models with different bioturbation mixing depths, constant and fluctuating sedimentation rates, and integration of pollution proxies that are in correlation with the industrial history of the coast. The different scenarios tested suggest an increase in accumulation rates although the diminution of the Nilotic source and point to the alteration of coastal land cover leading to increased sediment fluxes to the continental shelf. Other sedimentological parameters as grain circularity and end member modeling shade light on the modern sediment sources and the Nile Delta modification.