Abstract
In this paper, a computationally efficient shallow water model is developed for sediment transport in the Yangtze Estuary by considering mixed cohesive and non-cohesive sediment transport. It is firstly shown that the model is capable of reproducing tidal-hydrodynamics in the estuarine region. Secondly, it is demonstrated that the observed temporal variation of suspended sediment concentration (SSC) for mixed cohesive and non-cohesive sediments can be well-captured by the model with calibrated parameters (i.e., critical shear stresses for erosion/deposition, erosion coefficient). Numerical comparative studies indicate that: (1) consideration of multiple sediment fraction (both cohesive and non-cohesive sediments) is important for accurate modeling of SSC in the Yangtze Estuary; (2) the critical shear stress and the erosion coefficient is shown to be site-dependent, for which intensive calibration may be required; and (3) the Deepwater Navigation Channel (DNC) project may lead to enhanced current velocity and thus reduced sediment deposition in the North Passage of the Yangtze Estuary. Finally, the implementation of the hybrid local time step/global maximum time step (LTS/GMaTS) (using LTS to update the hydro-sediment module but using GMaTS to update the morphodynamic module) can lead to a reduction of as high as 90% in the computational cost for the Yangtze Estuary. This advantage, along with its well-demonstrated quantitative accuracy, indicates that the present model should find wide applications in estuarine regions.
Highlights
The Yangtze Estuary has been intensively influenced by human activities
Along the coast of China, the tidal amplitude is relatively stronger in the Hangzhou Bay, and reaches 1.9 m at the top of Hangzhou Bay, 14 of which exhibits good agreement with the results described by Hu et al [45], Ge et al
Given reasonable parameters, performs in reproducing the distribution demonstrate that the model, given well intransport reproducing of hydrodynamic processes, and isreasonable capable ofparameters, representingperforms the sediment in the the distribution hydrodynamic processes, is capable of representing the sediment
Summary
The Yangtze Estuary has been intensively influenced by human activities. The suspended sediment discharge to the Yangtze Estuary has reduced from 4.2 × 109 t·yr−1 during the period 1953–2002 to less than 1.0 × 109 t·yr−1 in the past decade [1]. Using MF ranging from 100 to 400, Guo et al [12,13] and Zhou et al [17] investigated the role of river flow, tidal asymmetry and salinity in the long-term (600–4000 years) evolution trends of idealized estuaries. It is still interesting to conduct intermediate-term (e.g., 10–30 years) simulations without resorting to the MF method Such interests are motivated by both the great progress of efficient numerical schemes as well as the improvement of computing hardware. The improved model was calibrated against field data (i.e., water level, tidal current velocity and SSC) in the Yangtze Estuary and Hangzhou Bay. Comparative numerical studies of key factors are conducted, including the bed resistance, erosion and deposition parameters and the initial bed sediment composition, as well as the Deepwater Navigation Channel (DNC).
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