Morphodynamical modelling of field-scale swash events

Abstract

In the present work, data for three single swash events are selected from those available for an accretive tide that occurred at Le Truc Vert beach (France) during a measurement field campaign at that location. These events are primarily chosen because of the different final bed change they produced, namely variable accretion, seaward erosion/landward deposition and variable erosion along the swash zone. These data are compared to results obtained from a ‘state-of-the-art’ numerical fully-coupled 1D morphodynamical shallow water solver, driven by measurements made of those events in the lower swash/inner surf zone.It is found that the hydrodynamics is reasonably well represented, although the computed results exhibit reduced maximum inundations in comparison with the observed ones. The model reproduces the correct order of magnitude of the morphodynamic change after each event, and sometimes the pattern of erosion and deposition, but this change is generally underestimated.Sensitivity analyses are conducted with respect to more uncertain physical parameters and assumed initial conditions. They suggest that initial spatial distributions for velocity and pre-suspended sediment concentration play a key role in the quantitative and qualitative prediction of the bed change.