Beach and Nearshore Morphodynamics of the Central-bulge of the Nile Delta Coast, Egypt

O.E. Frihy; E.A. Deabes
Beach-nearshore profiles, annually surveyed be-tween 1991 and 2010, combined with coastal processes are analyzed to assess changes in rate of shoreline position, seabed level, sediment volume and seabed grain sizes that developed after extensively protecting the central-bulge of the Nile delta coast with numerous engineering structures. This area including the Burullus-Baltim beach, 25 km long, is located on a very active littoral zone, which has expe-rienced widespread erosion of -5 m/yr, originally before construction of a series of engineering structures to stabilize the shoreline. These structures built in stages and include 17 detached breakwaters, 9 groins, 3 jetties, seawall and basalt riprap. The shift from beach erosion prior to the construc-tion of these engineering structures to accretionary tombo-los (18.9 m/yr shoreline advance; 36 cm/yr seabed accretion) and salient has successfully stabilized the coastline. Howev-er, erosion appeared downcoast of the detached breakwater system up to the Kitchener drain has resulted in the con-struction of additional groins. It is expected that sediment producing to the east along Gamasa embayment by the eastwardly unidirectional current will subsequently dimi-nish as a result of sand trapped by the constructed break-waters, built early in 1993. Unexpectedly, the active accre-tionary channel-mouth sandbars developed at the Kitchener drain mouth followed the construction of the nine groins have contributed to the problem of periodic sedimentation of this drain. In general, the study coastline exhibits a wide range of beach dynamics resulted from interactions of waves and shoreline orientation, hard structures and sedi-ment supply.
coastal processes; beach erosion; protective structures; sediment transport; estuarine sedimentation; detached breakwaters; coastal dunes
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