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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 = 0.23 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 = 0.7 mm; range of 0.41-3.3 mm), and relict mud to very fine sand (average Mz = < 0.051 mm; < 0.063 mm). Textural and compositional evaluations indicate that the coarse-grained relict sand (54 km2) 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 (RA) implies that eroded beaches would maintain a stable state following the sand-filling operation with a re-nourishment factor (Rj) 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. [ABSTRACT FROM AUTHOR]

Abstract: Landsat Enhanced Thematic Mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret geomorphological changes in the coastal zone between Kitchener drain and Damietta spit in the northeastern Nile delta previously recognized as a vulnerable zone to the effects of any sea-level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land. About 48 km2 of sand dunes, marshes, sabkhas and salt pans have been converted to productive fish farms. The main urban centers have expanded, and new urban centers (Damietta harbor and the New Damietta city) have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As the consequence of human activities the size of Manzala lagoon has been reduced to less than 50%. Short-term shoreline changes along the coast of the study area established from beach profile survey, spanning the years of 1990 to 2000, reveal longshore patterns of erosion versus accretion. The rate of shoreline retreat has increased in the downdrift side of Damietta harbor (−14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwater system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures. [Copyright &y& Elsevier]

Abstract: Beach profile equilibrium is the principal concept assumed by most numerical modelling. The response of beach profile configuration to natural and anthropogenic changes could be predicted to help in selecting the most appropriate engineering design required to mitigate coastal erosion and accretion alongshore. Thus, in order to apply coastal engineering projects, the predicted profile of equilibrium should be close enough to the measured profile. Therefore, before application of numerical modelling techniques, equilibrium expressions have to be validated at the study site. This research aims to assess the validity of the equilibrium profile concept on the Nile Delta coast based on beach profiles surveyed in 1990 from the main promontories; Abu-Quir Bay, the Rosetta promontory and the El-Burullus promontory. The results indicate that the equilibrium beach profile is consistent with the measured profiles at the study sites beyond 200 m distance offshore at −4 m depth. In contrast, the equilibrium status is not valid along the beach face at −1 m depth. Accreted beaches at Abu-Quir bay and Burullus promontory are characterized by wide berms and gentle beach face whereas eroded stretches at Rosetta promontory have a narrow berm and steep beach faces. The measured profiles are also compared with the exponential beach profile concept. An exponential hypothesis is not valid along the Nile Delta coast. Profiles measured at Abu-Quir, Rosetta and El-Burullus depart significantly from the exponential equation. Despite the fact that equilibrium expression can describe beach profiles along the Nile Delta, one equilibrium profile equation is not sufficient to assess all beach profiles. This can be explained as the morphology of beach profiles is subjected to some factors including; sediment characteristics, wave parameters and closure depth, which vary alongshore. Analysis of the validity of the equilibrium beach profile is recommended to get accurate results in modelling simulations and design the most appropriate engineering projects required for shore protection. [Copyright &y& Elsevier]

Beach profiles surveyed over a period of 18 y (1982 to 2000) at 41 sites were analyzed to assess beach changes, seabed scour, and grain sorting pattern fronting the 5 km long seawall built in 1991 to protect the Rosetta promontory from beach erosion, which had been retreating at a rate of -106 m/y. Although the seawall has succeeded in halting the recession, the shoreline shows adverse erosion at the leeside of the seawall ends (-14.4 m/y) associated with depth scour at a maximum of -0.50 m/y. The erosion along the promontory tip progressively decreases with longshore distance both to the east and to the southwest along the promontory flanks, reverting to accretion on both sides within the promontory saddles and yielding two nodal areas that represents zones where the sediment regime changes from erosion to deposition. Moreover, the seawalls have slightly altered the mean grain sizes of the beach sediment and seabed slope of the surf zone. The overall pattern of beach erosion and seabed scour results from wave refraction- induced longshore sediment transport along the promontory tip. The geographic correspondence between patterns of shoreline and seabed depth changes serve to refine boundaries of littoral subcells of the Rosetta promontory, including sediment paths, sources, sinks, nodal points, and zones of sediment transport convergence and divergence. The morphologic changes along this promontory reflect a combination of factors, including sediment availability, transport pathways from source areas, as well as the impact of protective structures at the Rosetta estuary. [ABSTRACT FROM AUTHOR]

Abstract: High resolution beach–inner shelf bathymetric profile surveys combined with wave data and sediment samples have been used to examine short-term morphological changes of the seabed at the eastern part of Abu Qir Bay. The profile survey covered ∼4.5 km alongshore and ∼9.5 km offshore to a 15-m water depth. These profiles were surveyed seven times between October 2001 and October 2002, showing changes during storms and the following recovery periods. Significant wave heights of storm waves (blown from the N and NNW) and fair weather waves (coming from the NW and NNE) were recorded between 2.0–5.0 m and <2.0 m, respectively. During storm periods, waves move sand from north to south and from the beach face and surfzone seaward to the upper shore face. The intervening periods between storms (swells of fair weather condition) are characterized by sediment redistribution from the northern or the southern parts toward the center of the bay. Mapping of computer-generated bathymetric surveys is used to interpret vertical seabed changes (erosion/accretion patterns) and to delineate sediment transport pathways. Linking this information with the spatial concentration of high intensity magnetic minerals (ilmenite and magnetite) in beach and seabed sediments helps to detect reversals in the directions of sediment transport to the north and to south, but with a general southward net pattern. The recognized outcrops of submerged rocks provide documented evidence that the shore-parallel late Pleistocene carbonate ridges, now subaerially exposed along the shore of Alexandria, extend further eastward on the seabed of Abu Qir Bay. [Copyright &y& Elsevier]

This paper focuses on the stability of the shoreline on the east side of the Rosetta promontory on the Nile Delta coast because this area was extremely eroded after construction of the eastern revetment on the east side of the promontory in 1991. Numerical models developed by the Danish Hydraulic Institute are used to calculate wave transformation from deep water to the nearshore region, compute littoral drift, and predict shoreline evolution along the east side of the Rosetta promontory. The results generated by the shoreline evolution model show that, in the case of applying no structures, the maximum retreat of the shoreline along the east part of the promontory is estimated to be 1405 m after 20 years. The minimum shoreline retreat along the east side of the Rosetta promontory was achieved with a system of five groins spaced at 800 m. [ABSTRACT FROM AUTHOR]