الفهرس 
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Abstract
Alexandria city is one of the oldest cities on the Mediterranean coast, and is an important tourist, industrial and economic centre. Its coastline extends for 140 km along the Mediterranean Sea, from Abu Qir in the east to AI-Alamein and Sidi Abdul Rahman in the west. It includes a number of beaches and harbors. Alexandria’s beaches are the main summer resort of the country and its harbors are the most important import/export link between Egypt and other countries.
In the recent years, Alexandria suffers from many erosion problems along its coastline, which result from natural and human activities in the coastal zone. Alexandria’s beaches have been eroded due to the coastal processes and sea level rise. The beach width gradually decreased due to the action of the waves and currents, and some beaches disappeared totaUy.
The main objective of this research is to study the effect of using Submerged Artificial Reefs (SARs) techniques to reduce the flooding and erosion problems due to wave action and wave induced current. The study was applied on Sidi-Bisher Beach, Alexandria, with a length of 400 m.
The objective of the research as was achieved through the following steps:
I) Collect the necessary dominate data required for this study such as (Bathymetry map and Seabed samples, Offshore wave data, and Wind data).
2) Validate the numerical modules ”MIKE 21” by using two published case studies. The first case is an artificial reef in the Bulgarian Black Sea coast. The second case is a parallel deep-water reef in the Scheveningen coast, Holland.
3) Use the ”MIKE 21 CAMS” model to simulate wave action, hydrodynamics phenomena of coastal areas, sediment transport, and morphological beach response after installation Artificial Submerged Reefs in Sidi-Bisher Beach, Alexandria.
4)
from the results obtained in this thesis, plans and cross-sections are used to illustrate the hydrodynamics and morphodynamics processes in the study area. In addition, predicative empirical relationships are proposed as preliminary engineering tool to assess shoreline response to submerged artificial reef.It was found that, the use of submerged artificial reef demonstrated good effectiveness in controlling the coastal beach erosion problems. The proposed crest level (Rc) is 0.5 meter or .lower below low water level. The relative crest width (crest width /wave length) ranged from 0.4 to 0.75. The level of protection is governed by the size and offshore position of the reef, so that the size of the salient or tombolo varies in accordance with reef dimensions. For a tombolo (Length of the structure / Distance from shoreline to structure = 1.6 to 2.0). Meanwhile, for a salient it was 0.8 to 1.3. In addition, expected natural sedimentation formed along the beach, which in turn will form a swimming area.