AUTHOR=Wang Jinyang , Dijkstra Yoeri M. , de Swart Huib E. 

TITLE=Turbidity maxima in estuarine networks: Dependence on fluvial sediment input and local deepening/narrowing with an exploratory model

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.940081

DOI=10.3389/fmars.2022.940081

ISSN=2296-7745

ABSTRACT=An estuarine turbidity maximum (ETM) results from various subtidal sediment transport mechanisms related to e.g. river, tides, and density gradients, which have been extensively analysed in single channel estuaries. However, ETMs have also been found in estuaries composed of multiple interconnected tidal channels, where the water and suspended fine sediments are exchanged at the junctions with possible occurrence of sediment overspill. The overall aim of this study is to understand the processes that determine the ETM dynamics in such channel networks. Specifically, focusing on the ETMs formation due to sediment transport by river flow and density-driven flow, the dependence of ETM locations in an idealised three-channel network on fluvial sediment input and the local deepening and narrowing of a seaward channel is investigated.
Sensitivity results show that, keeping river discharge fixed, a larger fluvial sediment input leads to the upstream shift of ETMs and an increase in the overall sediment concentration. Both deepening or narrowing of a seaward channel may influence the ETMs in the entire network. Furthermore, the effect of either deepening or narrowing of a seaward channel on the ETM locations in the network depends on the system geometry and the dominant hydrodynamic conditions. Therefore, the response of the ETM location to local geometric changes can only be understood by analysing the dominant sediment transport mechanisms. Additional to convergence of sediment transport mechanisms in single estuarine channels, ETM dynamics in networks is found to be strongly affected by net sediment transport between the branches of a network.
We find that considering the sensitivity of net sediment transport to geometric changes are needed to understand the changing ETM dynamics observed in a real estuarine network.