Coastal vulnerability assessment using GIS-Based multicriteria analysis of Alexandria-northwestern Nile Delta, Egypt

Abstract

This study intends to map the relative coastal vulnerability index (CVI) for the administrative governorates of Alexandria and adjacent Behera in the northwestern coastal margin of the Nile delta. In addition to other common environmental stresses, these governorates are under threat due to accelerated sea level rise induced from climate change. Of special interest is that the coastal margin of the study area is characterized by markedly constructing geology, morpho-dynamics and land surface topography that varies from low-lying (−3 m below MSL) to high land (~20 m height). Therefore, nine physical and geological variables influencing the vulnerability of the coast are used in this study, including land elevation, seabed/beach composition, beach type (dissipative to reflective), relative sea level, historical shoreline change, tidal range, significant wave height, shore protection measures, and land cover. Results obtained from performing multi-criteria analysis of GIS indicates that about 16.58%, 15.45, 42.03%, 18.16 and 7.78% of the shoreline is under very high, high, moderate, low and very low vulnerability respectively. Of great concern is that although the low-lying broad depression (−1 to −3 m below MSL) east and southeast of Alexandria is protected now by a combination of natural shore-parallel elevated ridges (up to 10 m) and artificial shore-parallel detached structures, it is likely to be accidently flooded by unexpected extreme storm or tsunami events at the lowest waterfront points.