Sediment-induced lateral circulation in tidal channels with high turbidity: A cross-sectional modeling study

Abstract

Despite extensive research on salinity-induced lateral circulation (SalLC) in tidal systems, the dynamics of sediment-induced lateral circulations (SedLC) remain largely unexplored. This study employs idealized cross-sectional modeling to investigate SedLC in a highly turbid tidal channel with lateral bathymetric variations. Lateral bathymetric gradients trigger sequential lateral gradients in tidal velocity, turbulence, suspended sediment concentration, sediment-induced density anomalies, and ultimately internal pressure. This sediment-induced lateral baroclinic forcing, combined with periodic tidal mixing, governs the onset, development, and dissipation of SedLC, exhibiting a clear flood-ebb symmetry. SedLC is characterized by a bottom turbidity current, surface countercurrent and center upwelling/downwelling currents, creating complex cross-sectional flows of water and sediment. A schematic of tidally influenced SedLC dynamics reveals three primary stages: strong SedLC with surface convergence during slack tides, moderate SedLC with surface divergence during accelerating tides, and weak SedLC with surface convergence during decelerating tides. Strong interactions occur between tidally symmetric SedLC and tidally asymmetric SalLC, with the circulations adding during flood and counteracting during ebb. This study enhances our understanding of baroclinically-driven lateral hydrodynamics in tidal systems, with potential implications for three-dimensional substance transport.