Within the framework of IGCP Project 389 an overview of the main factors controlling the development of coastal outline and morphology of the Egyptian Red Sea and Southern Gulf of Suez is given. Understanding such factors, especially those affecting the region in relatively recent times, is a prerequisite for any future development projects.
The Egyptian Red Sea coast is generally referred to as a typical rift coast. Based on distribution and the shape of coastline variations. the Egyptian coastline morphology and outline is subdivided genetically into three segments. Segement 1 is a tectonic coastline, localized in the area between Safaga and Gabel Zeit. Segment 2 is fluvially-dominated coastline associated with fault-cliffs in the stretching area between Safaga and Quseir. Segment 3 represents mixed tectonics, fluvial and land-erosion coastline comprising the area between Quseir and Hamata.
The main factors controlling the development and shape of coastal outline and morphology of the Egyptian Red Sea is given, and can be categorized into tectonic, climate and eustatic controlling factors.
Tectonically the Neogene and Quaternary extensional horsts and grabens (oblique, parallel and perpendicular to the present Red Sea shore) played a great role in the shoreline configuration during successive ages as well as in delineating the main trends of onshore headlands and offshore islands. Pliocene and post-Pliocene wrench and clysmic tectonics, mostly along faults perpendicular and parallel to the Red Sea, developed embayments and sharms as well as half domes acted as headlands adjacent to the shore. Halokinesis, possibly related to both wrench faulting and salt diapirism also played a certain role in shaping some of the topographic features observed along the shore. Rejuvination of neotectonic movements in the form of the 110o trending fractures and synsedimentary faults affecting the 120 and 4-6ky raised beaches developed straight fault-cliffs.
Alternating wet and dry climatic conditions played a role in supplying the coastal area with sediments that shaped its outline and topography. Alluvial fans running eastwards, and occasionally southeastwards when facing horsts are very pronounced in Plio-Pleistocene and Pleistocene times. Eastward extension of shore –sediments along structurally controlled grabens is now pronounced due to such clastic supply. During dry seasons in quaternary and recent times, evaporates and windblown sediments prevailed in low-lying areas and along structurally controlled bay shores respectively.
The eustatic sea level changes caused the progradation and retrogradation phenomena observed along the coast and the variously elevated mixed fluvial and reefs terraces and raised beaches. Also the eustatism played an important role in formation of land-erosion and fluvial coastline.
These results have implications for Public awareness of areas of recent active faulting and torrential flow along the Red Sea coastal areas, mentioned above, will certainly help in directing any future development projects and investments away of onshore areas of high risk due to natural hazards.