Numerical Modelling of Beach Morphodynamics in Post-nourishment Conditions—Case Study

The planning of effective and optimized beach nourishment interventions needs to be supported by numerical modelling predictions of the spatio-temporal evolution of the nourishment and the surrounding native beach. The topo-bathymetry of an urban oceanic beach was monitored immediately after a 1 million m3 sand nourishment and two months later. The coastal stretch has two types of backshore alongshore: dune and seawall. A process-based numerical model, XBeach—surfbeat mode, was applied to simulate the beach morphdynamics during the two months between surveys. The model was settled on the post-nourishment topo-bathymetry and forced with synoptic hydrodynamic data. Its performance was evaluated through indicators of impact and error. According to a frequently applied classification for numerical morphodynamic models, the model performance was evaluated as reasonable in the coastal stretch extreme sectors and good in the inner sector. The results suggest that the morphological evolution observed was not only due to the erosive incident waves but also to a readjustment to the beach natural profile following the sand deposition.