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Consequences of tidal dynamics on hydro-sedimentary processes are a recurrent issue in estuarine and coastal processes studies, and accurate tidal solutions are a prerequisite for modeling sediment transport, especially in macro-tidal regions. The motivation for the study presented in this publication is to implement and optimize a model configuration that will satisfy this prerequisite in the frame of a larger objective in order to study the sediment dynamics and fate from the Red River Delta to the Gulf of Tonkin from a numerical hydrodynamical–sediment coupled model. Therefore, we focus on the main tidal constituents to conduct sensitivity experiments on the bathymetry and bottom friction parameterization. The frequency-domain solver available in the hydrodynamic unstructured grid model T-UGOm has been used to reduce the computational cost and allow for wider parameter explorations. Tidal solutions obtained from the optimal configuration were evaluated from tide measurements derived from satellite altimetry and tide gauges; the use of an improved bathymetry dataset and fine friction parameter adjustment significantly improved our tidal solutions. However, our experiments seem to indicate that the solution error budget is still dominated by bathymetry errors, which is the most common limitation for accurate tidal modeling. [ABSTRACT FROM AUTHOR]

Tidal dynamics consequences on hydro-sedimentary processes are a recurrent issue in estuarine and coastal processes studies and accurate tidal solutions are a prerequisite for modelling sediment transport, especially in macro-tidal regions. The motivation for the study presented in this publication is to implement and optimize the model configuration that will satisfy this prerequisite in the frame of a larger objective to study the sediment dynamics and fate in the Red River delta to the Gulf of Tonkin from a numerical hydrodynamical-sediment coupled model. Therefore we focus on the main tidal constituents to conduct sensitivity experiments on the bathymetry and bottom friction parameterization. The frequency-domain solver available in the hydrodynamic unstructured grid model T-UGOm has been used to reduce the computational cost and allow for wider parameter explorations. Tidal solutions obtained from the optimal configuration were evaluated from tide measurements derived from satellite altimetry and show a strong improvement (compared to pre-existing tidal atlases) due to an improved bathymetry dataset and fine friction parameters adjustment. However, our experiments seem to indicate that the solution error budget is still dominated by bathymetry errors, which is the most common limitation for accurate tidal modelling. [ABSTRACT FROM AUTHOR]

The Gulf of Tonkin in the South China Sea receives huge inputs of dissolved and particulate suspended matter from the Red River. The river's discharge showed a strong temporal variability over the last decades both in terms of water and matter, from the seasonal to the decadal scales. This variability is associated to factors of natural and anthropogenic origins (dam building, sand dredging, water use, climatic variability, from extreme events (typhoons) to the interannual (ENSO) and long term evolution...). Understanding the functioning and variability of transport and fate of sediment from the Red River to the Gulf of Tonkin is essential in order to assess their impact on sediment erosion and accretion therefore on the evolution of seabed and coastline. Our objective is to understand the influence of ocean dynamics, from the submesoscale to the large regional scale, on this transport and fate and to examine their response to various forcings. For that, we use a combination of coupled modeling tools and in-situ observations.In-situ measurements were performed in two distributaries at different seasons and tidal regimes. Sampling methods as well as our findings on double Estuarine Turbidity Maxima and tidal-induced salinity intrusion, will be presented. The spectral tidal model T-UGO is used to perform fast test on tidal boundary conditions. Results of the impacts of bathymetry, roughness and friction coefficients on tidal solutions are presented. The hydrodynamic ocean model SYMPHONIE is coupled with the sediment transport model MUSTANG. Simulations are performed over the 2009-2017 period using a varying resolution bi-polar grid refined over the Red River mouth region. Results concerning riverine and ocean dynamics, sediment transport and their variability will be presented, with comparison with in-situ measurements to assess the ability of the models to represent coastline morphodynamics and ocean dynamics. [ABSTRACT FROM AUTHOR]