ORIGINAL Omran E. Frihy Æ Moheb M. Iskander Abd El Moniem A. Badr Effects of shoreline and bedrock irregularities on the morphodynamics of the Alexandria coast littoral cell, Egypt Received: 4 December 2002 / Accepted: 5 April 2004 / Published online: 18 May 2004 Ó Springer-Verlag 2004 Abstract Beach-nearshore profiles combined with beach and surficial sediment samples were analyzed in con- junction with wave, current, littoral drift and sea-level data to determine the effect of bedrock on morphody- namic processes within the littoral zone of Alexandria on the Mediterranean coast of Egypt. This 14.5-km-long littoral cell is bounded by pronounced embayments and pocket beaches separated by headlands which prevent bypassing of beach sands, in effect making this cell a large, semi-closed basin. The compartmented nature of this cell acts together with the rough irregularity of the rocky seafloor to trap a thin veneer of sediment (<3 m thick), showing proportional mixing betwee‘n two sedi- mentary provinces. A modern fine-grained sediment fa- cies consisting of mixed carbonate/siliciclastic sand flanks most of the nearshore zone down to a depth of 8– 10 m. Beyond this depth, considered to be the depth of closure, a relict late Pleistocene to mid-Holocene coarse- grained facies composed of biogenic carbonate sand is found. Along a short section of the coastline (km 3–6), the coarser sediment also occupies the nearshore zone. Over most of the study area the two sediment types are mixed in various proportions, largest mixing coinciding with poorest sorting. Profile analyses revealed seasonal changes in sediment volume along the coast which clo- sely follow the cyclicity of seasonal changes in wave climate. The present shoreline orientation, headlands and rough, irregular rocky seabed are reflected in the erosion/accretion pattern, sediment characteristics, and the reversibility of longshore currents and littoral drift. Although there is a marked deficiency in the sediment balance, the sand budget for this cell, including artificial material (2.339*10 6 m 3 ) has increased slightly by 0.041*10 6 m 3 year )1 as a result of engineering works carried out to widen the coastal road (Corniche). In addition to the physical properties of the bedrock (degree of induration), the accelerating sea-level rise during the Holocene and human influences, the modern morphology of the coast, the erosional seabed features in the nearshore zone, and the texture of seabed sedi- ments are all controlled by the original geometry of the coast which consisted of an elevated subaerial ridge. Introduction The ancient city of Alexandria is located immediately west of the Nile delta and was founded by Alexander the Great in 332–331 B.C. Geomorphologically, Alexandria is built on a narrow coastal plain consisting of Pleisto- cene carbonate-sand ridges (Fig. 1A). This coastal plain represents the most eastern part of ridge #2 (Abu Sir), which has been assigned a ‘‘main Monasterian’’ age (Shukri et al. 1956). It is backed to the south by various land-use units including urban areas, Mariut lake, in- land depressions, desert, and agricultural land (Shukri et al. 1956; Warne and Stanley 1993). Alexandria is considered today one of the oldest, continuously existing cities of the world. It is the second largest city in Egypt and one of the major ports in the Mediterranean Sea, besides being an important com- mercial, business, industrial and cultural center. Fur- thermore, a number of submerged archeological sites have recently been discovered off the Alexandria coast- line, which is also the principal seaside resort of Egypt, attracting about two million visitors every summer. The city hosts four harbors: El Diekhila Harbor, the Western and Eastern harbors and Abu Quir Harbor (Fig. 1B). Generally, the 100-km-long coastline of Alexandria is oriented SW–NE and is bordered by a highway known as the Corniche. The coastline can be divided into three sectors based on morphological character: resort bea- ches to the west of Alexandria beginning at El Agami, the Western Harbor basins, and the resort beaches from El Silcila to the Abu Quir headland (Fig. 1B). These sectors are separated by major headlands at El Agami, O. E. Frihy (&) Æ M. M. Iskander Æ A. E. M. A. Badr Coastal Research Institute, 15 El Pharaana Street, El Shallalat, 21514 Alexandria, Egypt E-mail: Frihyomr@link.net Geo-Mar Lett (2004) 24: 195–211 DOI 10.1007/s00367-004-0178-x