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Previous studies have indicated that the Nile River deltaic plain is vulnerable to a number of aspects, including beach erosion, inundation, and relatively high rates of land subsidence. This issue motivates an update and analysis of new tide-gauge records, from which relative sea-level changes can be obtained. Estimated rates from five tide gauges are variable in terms of magnitude and temporal trend of rising sea level. Analysis of historical records obtained from tide gauges at Alexandria, Rosetta, Burullus, Damietta, and Port Said show a continuous rise in mean sea level fluctuating between 1.8 and 4.9 mm/year; the smaller rate occurs at the Alexandria harbor, while the higher one at the Rosetta promontory. These uneven spatial and temporal trends of the estimated relative sea-level rise (RSLR) are interpreted with reference to local geological factors. In particular, Holocene sediment thickness, subsidence rate and tectonism are correlated with the estimated rates of relative sea-level change. From the relatively weak correlation between them, we presume that tectonic setting and earthquakes, both recent and historical ones, contribute more to accelerated RSLR than that of dewatering and compression/ dewatering of Holocene mud underlying the Nile Delta plain. As a result, large areas of the coastal plain have been subsided, but some sectors have been uplifted in response to tectonic activities of thick underlying older strata. Projection of averaged sea-level rise trend reveals that not all the coastal plain of the Nile Delta and Alexandria is vulnerable to accelerated sea-level rise at the same level due to wide variability of the land topography, that includes low-lying areas, high-elevated coastal ridges and sand dunes, accretionary beaches, and artificially protective structures. Interaction of all aspects (tectonic regime, topography, geomorphology, erosion rate, and RSLR rate) permitted to define risk areas much vulnerable to impacts of sea incursion due to accelerated sea-level rise.

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Textural and compositional characteristics of beach and bottom sediments collected from the beach-continental shelf of Alexandria region on the Mediterranean coast of Egypt were examined to search for quality nourishment borrow material, and to initially assess its compatibility with the existing native beaches. Sediment characteristics and carbonate content combined with analyses of coastal processes (waves and currents) and seabed morphology are also explored to interpret sediment transport pathways. Three sediment types composed of carbonate material are identified on the Alexandria shelf based on their texture and compositional characteristics. These are: Late Holocene to modern fine to medium sand (average Mz ¼ 0.23 mm; mm; range of 0.063-0.4 mm), a relict late Pleistocene to mid-Holocene shelly coarser material, coarse to very coarse sand (average Mz ¼ 0.7 mm; range of 0.41-3.3 mm), and relict mud to very fine sand (average Mz ¼ < 0.051 mm; < 0.063 mm). Textural and compositional evaluations indicate that the coarse-grained relict sand (54 km 2 ) is locally found just seaward of the Alexandria Metropolitan area between water depths of $10 and 70 m; corresponds to 1 to 10 km distance from the coastline, and could be used as a nourishment and borrow material for eroded beaches of Alexandria that have experienced prolonged sediment deficiency combined with anthropogenic influences. Compatibility analysis indicates that the characteristics of the defined borrow material and those of the native beach are generally compatible with each other. With respect to the quality standards, the borrow material is similar to and slightly coarser than the native beach sand and also matches the same range of sorting (0.25-2.37 Ø) and carbonate content (8.0 to 99.9%); therefore it is compatible to use as a sand source for beach nourishment. Moreover, estimated overfill factor (R A ) implies that eroded beaches would maintain a stable state following the sand-filling operation with a re-nourishment factor (R j ) of 0.39.Our observations indicate that shelf sediments, both relict and modern, are displaced northeasterly in the alongshore and offshore directions by the N and NW wave-induced currents in conjunction with the counter-clockwise geostrophic East Mediterranean current. These sediments are reworked and deposited as mixed carbonate and biogenic sands on the irregular rocky seafloor of the submerged ridges that characterize the inner shelf and are considered as the major source of sediment in the study region.