We present a model for the morphodynamics of tidal basin-inlet-delta systems at the centennial time scales. Tidal flow is calculated through a friction dominated model, with a semi-empirical correction to account for the advection of momentum. Transport of non-cohesive sediment (sand) is simulated through tidal dispersion, i.e., without explicitly resolving sediment advection. Sediment is also transported downslope through a bed elevation diffusion process. The model is compared to a high-resolution tide-resolving model (Delft3D) with good agreement for different hydrodynamic and sedimentary settings. The model has low sensitivity with respect to temporal and spatial discretization. For the same spatial resolution, the model is about five orders of magnitude faster than tide-resolving models (e.g., Delft3D), and about three orders of magnitude faster than tide-resolving models that use a morphological acceleration factor. This numerical efficiency makes the model suitable to assess long-term changes of large coastal areas. The model's simplicity makes it suitable for coupling with other physical, ecological, and socio-economic dynamics.for tide-dominated transport, which also has a simple structure that will facilitate the inclusion of additional processes (i.e., river flow, waves, sand/mud dynamics, ecological processes) in the future.The bottleneck that increases the computation time of models for tidal morphodynamics is the need to solve the intra-tidal modulation, which generally requires time steps on the order of seconds for stability criterion. One approach to reduce this computation time is to only consider the net effect of a tidal cycle on the sediment transport without solving the intra-tidal variability. The basic idea of this approach is that the bidirectional tidal motion can be parameterized as a diffusion mechanism, here referred to as tidal dispersion [11,12]. This simplification is analogous to the use of a turbulent diffusion to simulate the bidirectional advective motion that takes place at spatial and temporal scales smaller than those simulated. The resulting coefficient for the tidal dispersion is very large, on the order of 100-1000 m 2 /s, which allows to transport large amounts of sediment and to effectively simulate channel network formation and evolution.The tidal dispersion model still requires to calculate a tide-averaged velocity from which to estimate the sediment resuspension and the dispersion coefficients. Di Silvio et al. [12] suggested to use a steady-state friction-dominated model for the tidal hydrodynamics. With this assumption the governing equations reduce to a Poisson problem. Thus, the combined hydrodynamic and sediment transport models constitute a robust system that can be solved efficiently [12]. The tidal dispersion model was initially proposed to simulate the evolution of a microtidal lagoon [12,13]. The model successfully reproduced the ontogeny of a realistic tidal network starting from a flat configuration. Unlike previous models, however, the model did not simu...
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