The Northwestern Mediterranean Coast of Tunisia: Wave Processes, Shoreline Stability and Management Implications

Abstract

The 10-km long coastline of the Tabarka–Berkoukech on the northwestern Mediterranean coast of Tunisian is characterized by marked morphological features, including embayments, long extensions, headlands, pocket beaches, sand dunes and sea-cliffs. The undulated nature of this coastline has permit sand, originated from three rivers, to confine between headlands, embayments, pocket beaches and the downdrift leeside of Tabarka Harbor breakwaters. Wave-related coastal processes simulated by STWAVE model together with the analysis of aerial photographs are jointly combined to evaluate degree of stability of this coastline. Analysis of aerial photographs dated 1963 and 2001 (38 years) using the Digital Shoreline Analysis System document significant beach changes in the sandy beaches. Maximum accretion occurs downdrift of Tabarak Port (3.8 meter/year), followed eastward by a minor erosion of −1.5 meter/year at El Morjene beach. The morphological characteristics of this coastline exhibit a wide range of beach dynamics resulted from interactions of waves, shoreline orientation and sediment supply. Pattern of longshore sediment transport direction has been deduced from the interplay between incident waves versus average shoreline orientation (angle of incidence). Results indicate that the W and NW waves are responsible for the generation of the sediment transport to the east throughout the year. This transport process is also accompanied with a net westerly reversals induced from the N and NE waves. Such wave reversibility, in general, generates a long-term equilibrium between the opposing east and westward sand movement within the coastline, yielding to an effective zero net littoral drift with a minimum sand loss resulting in stable beaches. Collectively, results obtained are jointly discussed in the context of sustainable management of this coastline.