Modelling the effect of kelp on sand dune erosion

Large parts of the Australian coastline are surrounded by nearshore aquatic vegetation, such as kelp or seagrass. Although it is widely accepted that vegetation plays an important role in dissipating wave energy and reducing current magnitudes, there is a limited understanding on how this affects coastal morphology. Consequently, most coastal models can currently not account for this effect. The aim of this work is to assess the effect of flexible aquatic vegetation, kelp in particular, on sand dune erosion using a process-based model, XBeach. The model is validated with experimental data obtained from literature, showing that XBeach can accurately model the measured wave evolution. Moreover, the model is able to reproduce dune erosion volume reasonably well. To investigate the effectiveness of kelp in mitigating storm-induced erosion, a series of synthetic storm events were simulated for a beach in northern Tasmania (Australia) that has suffered from erosion in the past. Model scenarios were focused on climate change effects, such as sea level rise and change in kelp forest cover. The results of this modelling study suggest that, across a range of climate change scenarios and storm intensities, the presence of kelp may have a significant effect on coastal stability during storm events.