Sedimentary Dynamics of the Bay of Béago in Yopougon (Abidjan, Côte d’Ivoire): Morph-Bathymetric, Lithological, and Morphoscopic Approaches

Abstract

The bay of Béago, like the entire Ebrié lagoon, is considered to be a relatively stable environment and an environment conducive to anthropogenic activities, of both biological and socio-economic interest. However, the discharge of water and garbage caused by the population as well as the dredging of sand can pollute and degrade the bay of Béago. The objective of this study is to characterize the sediments and conduct the bathymetric study of the bottom of this bay. Morphologically, the lagoon has a regular relief that is rugged in places and a strong depression to the northeast and northwest. It has the greatest depths of more than 18 m and shoals at the level of the banks. The bathymetry of the bay of Béago highlights three types of channels: the “V” “U” and intermediate channels. These channels reflect intense erosion, a balance between the agents of accumulation and erosion, and an imbalance between the agents of erosion and accumulation. The particle size study of the sediments highlights two types of lithologies: the sandy facies and the muddy facies. Two main classes are contained in the sands. These are coarse sands (20%) and medium sands (80%). Most of the sediment was deposited in a fluvial environment from a variety of feeder sources, including rivers and coastal dunes. Quartz grains have various shapes (angular to sub-angular, rounded to sub-rounded, and dull rounds, the most dominant of which are those of sub-angular) with a more blunt shiny appearance, which indicates transport in an aqueous medium over a relatively short distance. The samples of vases taken made it possible to determine two lithologies: silts and clays. All of these vases are dominated by silts with a rate of 87.5% compared to 12.5% of clays.