THE NILE LITTORAL CELL AND MAN'S IMPACT ON THE COASTAL ZONE OF THE SOUTHEASTERN MEDITERRANEAN

摘要

Man's intervention with coastal processes takes many forms. However, the most serious large scale, long term coastal erosion results from the interception by dams of rivers supplying sediment to the coast. This loss of sediment may have catastrophic effects along coasts where streams discharge directly into coastal waters. The Nile littoral cell is an impressive example of the effect of dams on coastal erosion. The Nile littoral cell is located in the southeastern Mediterranean Sea and extends 700 km from Alexandria, Egypt in the south to Akko, Israel in the north. The sediment load from the Nile River was deposited along the submerged portion of the delta, where it was sorted and transported to the east by the prevailing waves and by currents of the counterclockwise east Mediterranean gyre that commonly flows at about 50 cm sec over the delta. Prior to 1964, the turbid plume of the flood waters of the Nile River could be traced along the Mediterranean coast for over 700 km to the shores of Lebanon. Fine silt and clay sized material were carried easterly and into deeper water, while sand is carried easterly along the shelf and shore as far as Haifa Bay. Until 1964, the major sediment source of the littoral cell was the Nile River. Construction of the High Aswan Dam, which began filling in 1964, has resulted in a near absence of Nile River flow into the Mediterranean and a corresponding complete loss of the Nile River as a source of nutrients to coastal waters, and as an active sediment source for the delta and the coastline of the Nile littoral cell. As a result, the Nile Delta is now subject to severe erosion in a number of localities.