Hydrosedimentary dynamics and morphological evolution of the Abidjan harbor (Côte d’Ivoire): Implications for sustainable port management

Lagoons are environments conducive to the development of significant biodiversity. This characteristic gives them considerable economic value (fisheries, tourism, navigation). However, certain processes such as the silting up of bays, changes in water circulation, the presence of vegetation and the transport of sediments in the Vridi Canal are causing the lagoons to gradually fill up. This filling is impacting the morphology of the harbour bed. This study therefore aims to present the morphology of the bed and characterise the sediment dynamics of the port harbour of Abidjan. Bathymetric surveys were conducted in 2019 and 2023 by the hydrographic department of the Port Autonome d'Abidjan (PAA) in order to understand the impact of hydro-sedimentary processes on the morphological evolution of the harbour. Analysis of the bathymetric maps revealed that the harbour basin has a fairly irregular relief with depths of up to -26 m in 2019 and -95 m offshore in 2023. The characterisation of the channels revealed bathymetric profiles in the shape of a ‘V’, ‘U’ and intermediate shapes. Overlaying the bathymetric maps of the harbour basin from 2019 and 2023 revealed that the harbour basin underwent significant geomorphological changes between 2019 and 2023, with an estimated sediment budget of approximately +4 million m³, or an average of +800,000 m³/year. The rate of infill is estimated at 0.7 m/year in the harbour basin.