Abstract
River networks and estuaries are very common in coastal areas. Runoff from the upper stream interacts with tidal current from open sea in these two systems, leading to a complex hydrodynamics process. Therefore, it is necessary to consider the two systems as a whole to study the flow and suspended sediment transport. Firstly, a 1D model is established in the Pearl River network and a 3D model is applied in its estuary. As sufficient mass exchanges between the river network and its estuary, a strict mathematical relationship of water level at the interfaces can be adopted to couple the 1D model with the 3D model. By doing so, the coupled model does not need to have common nested grids. The river network exchanges the suspended sediment with its estuary by adding the continuity conditions at the interfaces. The coupled model is, respectively, calibrated in the dry season and the wet season. The results demonstrate that the coupled model works excellently in simulating water level and discharge. Although there are more errors in simulating suspended sediment concentration due to some reasons, the coupled model is still good enough to evaluate the suspended sediment transport in river network and estuary systems.
Highlights
As a link between marine environments and rivers, estuaries are characterized by a variety of complex and complicated processes [1]
The results show that the model skill score for sediment concentration is lower than that for water level and discharge
The relationship expression of water level at interfaces of 1D model and 3D model is strictly deduced by utilizing the relations between the water level and discharge at junctions
Summary
As a link between marine environments and rivers, estuaries are characterized by a variety of complex and complicated processes [1]. In the researches on hydrodynamics and suspended sediment transport in this region, numerical model is no doubt a highly efficient and low-cost method to describe estuarine flow and sediment transport processes in recent decades. The 3D model is more useful in evaluating the coastal flow and sediments movement due to the vertical circulations. If both the upstream river network geometries and the downstream tidal currents in the estuary are complicated, application of individual 1D or 3D model for the river and the estuarine area will result in either an inadequate representation of these processes (in case of 1D) or a computationally inefficient method (in case of 3D) [4]. It is necessary to take upstream river network and downstream estuarine system as a whole in one modelling system, to resolve the relevant physical processes in a consistent way
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