Modelling Sediment Transport in the Swash Zone

Abstract

The swash zone is the part of the beach that reaches from the limit of wave run-up until the limit of wave run-down. It is recognized as being a dynamic area of the nearshore region, characterized by strong and unsteady flows, high turbulence levels, large sediment transport rates and morphological changes on a small timescale. Due to the complexity of the processes taking place in the swash zone, there are still great uncertainties about the driving forces for sediment transport. Morphodynamic process-based numerical models tend to overestimate the seaward directed sediment transport in the swash zone, especially for mild wave conditions. The main objective of this thesis is to obtain insight in the hydrodynamic processes responsible for sediment transport in the swash zone, and to use this knowledge to optimize a morphodynamic numerical model (XBeach) for simulating swash zone physics. First, an extensive literature review is carried out to provide the physical base. Second, a number of (theoretical) linear profile simulations are conducted to provide insight into the simulated swash characteristics for different beach states, and to assess the effect of including a number of swash processes (e.g. turbulence or groundwater flow) in the simulations. Third, measurements obtained during a field experiment in Le Truc Vert (France) are used to verify three hydrodynamic modelling approaches and two sediment transport models.