LONGSHORE VARIABILITY IN DUNE EROSION - MODELLING THE COUPLING BETWEEN OUTER BAR MORPHOLOGY AND DUNE EROSION USING XBEACH

Abstract

Longshore variability in dune erosion: modelling the coupling between outer bar morphology and dune erosion using XBeach. Dunes are often a first line of defence against the against storm impact in coastal regions. It is therefore important to understand the driving processes of dune erosion. As Castelle et al. (2015) observed in the field, longshore variation in dune erosion can be coupled to the outer bar morphology. The use of process-based numerical models can help expand our knowledge of coastal systems, when acquiring field data is difficult due to the extreme conditions during storms. XBeach is developed for this purpose. In this research, XBeach is used to study the impact of a crescentic outer bar on a longshore uniform dune topography based on Egmond aan Zee, the Netherlands. Different storm conditions with regards to wave height and angle of incidence are tested. These conditions are simulated in XBeach using both the multi-dir method (Roelvink et al. 2009) and the single-dir method (Roelvink et al. 2018), resulting in some interesting observations.