Development and validation of a three-dimensional morphodynamic modelling system for non-cohesive sediments

Abstract

The morphology of estuaries and rivers changes constantly due to the dynamic imbalance between the forcing actions (e.g. river flow, tides, surface waves and wind) and the sedimentary reactions. Understanding and predicting these changes are very important for an scientific-based, sustained management of these systems. Morphodynamic process-based numerical models can be used for this purpose. The development and validation of a new three-dimensional unstructured grid morphodynamic modelling system, MORSELFE, aiming at simulating short-term morphological evolutions of estuaries and sandy rivers (temporal scale of days to month), are presented. MORSELFE couples a three-dimensional hydrodynamic model, with an advection–diffusion transport model for the suspended sediments, an empirical formula for the bed load, and a bed updating module. The model considers the simulation of non-cohesive sediment and does not account for wave effects. A new approach is proposed to compute the erosive fluxes, which adapts them to the vertical grid resolution. The use of unstructured grids and the implementation in parallel mode make MORSELFE particularly adapted to engineering applications. The model was assessed and validated against analytical and experimental test cases, also allowing the inference on the optimum choice of the model parameters and variables.