ASHDOD PORT'S EFFECT ON THE SHORELINE, SEABED AND SEDIMENT

Abstract

During its 35 years of existence, Ashdod Port, Israel, caused changes to its physical environment. Analysis of aerial photographs and bathymetric surveys show that the port served as a sediment trap, blocking the natural northward sediment transport. Between 1958, prior to the port construction, and 1992 the beach to the south of the port underwent accretion which increased in magnitude from zero, at a distance of 2.5 km south of the port, to more than 100 m near the main breakwater. On the northern side of the port the shoreline was stable during that period. It was found that the beach north of the port did not suffer erosion because the sand of that beach was mined for building purposes prior to the port's construction. When the port was built, it was already a rocky beach. Comparison between bathymetric surveys, which were carried out in the vicinity of the port, at various periods since prior to its construction until 1995, show that the port has trapped some 4.5 million m3 of sediments on its southern side. Of these, about 2.2 million m3 were deposited during the period of 1985-1995. It is estimated that more than half of this volume was deposited in 1992 during three very severe storms. On the basis of the depositional pattern in the vicinity of the port, and assumptions related to the net longshore sediment transport, it is estimated that more than half of the sediment volume bypasses the port northward.