Beach and Nearshore Features Along the Dissipative Coastline of the Nile Delta, Egypt

Abstract

Rhythmic beach and nearshore features along the Nile Delta coast are investigated from aerial photographs, beach profiles and field observations. Beach cusps and underwater sand bars of parallel and crescentic types, typical of tideless seas are delineated. Aerial photographic analysis and field observations show that many beaches west of Abu Quir headland, contained long crescentic bar systems. In contrast, parallel longshore bars exist along the delta extending from east of Abu Quir to Port Said. The parallel bar systems along the Nile Delta are generated by the dominant eastward longshore current and the associated littoral drift. The crescentic bars west of Abu Quir headland at Alexandria are associated with rip currents and negligible littoral drift. Application of the surf-scaling paramete (ϵ) indicates a fully dissipative state for the Nile Delta coast and moderate dissipation west of Abu Quir. The surfscaling analysis and the configuration of the beaches suggested that the study area can be generally divided into two morphodynamic zones. The first zone, the delta coast has a gentle slope varying from 1:50 to 1:100, a smooth wide beach face mainly composed of quartz sand discharged from the Nile and characterized by parallel bars. The beach sand is fine to medium, mainly derived from the Nile River. The second zone is located west of the delta, along the Alexandria waterfront and the beaches further west. This zone is characterized by a relatively steep slope of 1:30 with pocket and embayed shorelines composed of biogenic sand with rocky shoals except for the western part which is of uniform alignment. with medium to coarse oolitic carbonate sand beaches dominated by crescentic bars, The oolitic grains are derived from the adjacent Pleistocene limestone ridges which run parallel to the western coast of Alexandria.