Longshore Sediment Transport Rate Estimation near Harbor under Low and High Wave-Energy Conditions: Fluorescent Tracers Experiment

Abstract

The main objective of this research was to contribute to the comprehension of actual physical processes responsible for sand accumulations at the Cap Djinet harbor entrance and its immediate surroundings. This maritime infrastructure was implemented at the nearshore area of a sandy cap situated between the mouths of two wadis and bordered by sandy barred beaches classified in the microtidal intermediate beaches category. This stretch of coastline had never been investigated before, and given the importance of sedimentary transfer, an original dual experimental and modeling approach was adopted by using fluorescent tracers to identify sedimentary rates and flux directions under variable wave-energy conditions and testing the adaptability of four well-known formulas for longshore sediment transport predicting local sediment transport conditions. Offshore wave data covering the experimental period were extracted from the Wavewatch III database and input into a two-dimensional (2D) refraction–diffraction model to predict the nearshore wave conditions. The fluorescent tracing results revealed a convergence of sedimentary transfers toward the harbor for any offshore swell regime, with transfer rates reflecting conditions of low and high energy but remaining site specific to the morphodynamic state of each beach. A comparison of results of measured and predicted sedimentary fluxes indicated that the Coastal Engineering Research Center (CERC) model yielded satisfactory results under high-energy conditions and that the Kamphuis model was valid under low-energy conditions.