Effects of islands on sediment transport in a narrow strait: Strengthening or choking?

Straits are important pathways for material exchange in the ocean, and understanding the dynamics of these conduits is critical for quantifying regional and global sediment balances. Many straits contain complex island chains, yet little is understood about the role of these mid strait islands in controlling hydrodynamics and sediment dynamics. We examine the impact of island distribution on sediment transport in the Bohai Strait using in-situ observations and numerical modeling. Observations of water level, velocity, and suspended-sediment concentration around an archipelago in the Bohai Strait demonstrated that increases in water velocity and sediment flux were generated by Island topography. The model results showed that the distributions of current and sediment transport in the Bohai Strait were mainly controlled by the barotropic gradient force, and the presence of islands increased the sea level height difference across the axis of the strait. This change in sea level height enhanced the current velocity between islands, improved the efficiency of suspended sediment transport, and thus increased suspended sediment transport. Altering the width/average depth ratios of the channel and distributions of islands affected the total suspended sediment flux. Through many numerical experiments, we proposed a simple parametric equation, hoping to provide some reference for the simulation of sediment transport in complex topography.