Assessment of natural coastal hazards at Alexandria/Nile Delta interface, Egypt

Abstract

Recent in situ fine-grid waterfront survey integrated with inland elevation, nearshore depth soundings and wave data are incorporated into procedures for determining natural hazards, which are prevailing or expected at Alexandria/Nile delta interface on the Mediterranean Sea of Egypt. The hazards being assessed include wave runup height, inundation distance, rates of sea-level rise and shoreline change rate. The lateral variation of the hazard values along ~133.8 km which is the total length of the study coast helps with identifying six low-lying vulnerable spots with different potential hazards. Three vulnerable spots [2.3–2.5 m above mean sea level (msl)] are identified at Alexandria, specifically at the Eastern Harbor, Lauran and Mandara-Montaza beaches. In addition, three other low-lying spot areas are distinguished at Idku resort beach (1.0–1.5 m above msl) and on both sides of the western and eastern flanks of the Rosetta Nile promontory (1.0–1.2 m above msl). Detailed analysis of spatial and cross-shore transects generated from near shore/land elevation map marks contrasting elevations that vary from low-lying (− 3 m below msl) to high elevated carbonate ridges parallel to the shore (∼20 m above msl). The high-elevated coastal ridges underlying Alexandria’s seafront—maximum elevation of 12 m above msl—in addition to other protection elements are acting together as a natural quasi-barrier to mitigate sea flooding that may in turn affect the historical low-lying depressions located east and southeast of the city.