Analytical Investigation of Sediment Transport Dynamics and Their Implications for Dredging Planning in the Cross River Estuary

Understanding sediment transport dynamics in estuarine environments is fundamental to evidence-based dredging planning and the maintenance of navigable waterway depths. This study conducts an analytical investigation of sediment transport processes in the Cross River estuary between Calabar and the Atlantic approaches, using a combination of field measurements and hydrodynamic-sediment transport numerical modelling. Field data collection involved installation of acoustic Doppler current profilers and suspended sediment samplers at five cross-sections of the estuary over two seasonal measurement campaigns covering both wet and dry seasons. Collected data were used to calibrate and validate a two-dimensional depth-averaged hydrodynamic and sediment transport model of the estuary. Model simulations were used to evaluate sediment deposition patterns, quantify sedimentation rates at the navigation channel, and assess the sensitivity of sedimentation to seasonal discharge variations. Results indicate that sedimentation rates in the navigation channel are substantially higher during the wet season due to increased fluvial sediment supply from the Cross River catchment. The model identifies specific channel segments where sedimentation rates are two to three times the estuary mean, providing a basis for targeted maintenance dredging prioritisation. The study contributes a validated numerical model of Cross River estuary sediment dynamics, which represents a significant advance over previously available information. Keywords: sediment transport, Cross River estuary, hydrodynamic modelling, dredging planning, sedimentation rates