Wave climate and morphosedimentary characteristics of the Kenitra–Bouknadel sandy coast, Morocco

Abstract

The Bouknadel–Kenitra 20-km sandy coastline is of strong interest from the perspectives of beach amenity, tourism and erosion issues. This section of the Moroccan coastline has only received little attention in the literature so far and morphosedimentary characteristics as well as wave climate are poorly understood. The present paper provides the first extensive description of both wave climate and alongshore variability in the morphosedimentary behavior of these wave-dominated beaches, combined with accurate topographic surveys, 9-year long global wave model output time series and subsequently driven empirical longshore drift formula and shoreline change measurements from aerial photographs. Results show that the coast is mainly exposed to high-energy low steepness NW waves (mostly during the October–March period) generated in the North Atlantic by eastward traveling low pressure systems. Given the shoreline orientation, northward and southward longshore drift components generated by this wave regime nearly balance. In contrast, the lower-energy higher steepness N–NW wave regime (April–September period) contributes to an overall quantity of sand being transported southward similar to the yearly averaged net longshore drift. Beaches are mostly of the double-barred intermediate type. The southern beaches exhibit persistent rhythmic sandbars and rather steep beachface while the northern beaches are close to the dissipative state despite all the beaches are exposed to the same wave regimes. Beach states predicted using the Dean’s number roughly match these observations. While previous studies elsewhere had shown that inherited geological factors may overwhelm contemporary dynamics in the determination of beach states, here differences are attributed to coastal protection works that appear to be important additional determinants of beach morphology.