Performance Evaluation of XBeach for Seawater-Aquifer Interaction Simulation in Swash Zone of Gravel Beach: An Attempt to Reduce the Phase Errors

The swash zone and its processes are very important in a beach system due to their significant effects on beach hydrodynamics, morphodynamics and ecosystems, including beach flows, aquifers, and sediment transport. It is important to develop efficient numerical models to evaluate hydrodynamic-morphodynamic processes, particularly in the swash zone. XBeach is a numerical model for beach simulations. Despite substantial advances, XBeach remains yet to be further developed since it is inefficient in modeling interactions between the aquifer level and seawater. This study aimed to cope with XBeach phase errors in the aquifer (seawater-aquifer interaction) estimations leading to an inaccurate simulation of hydrodynamic-morphodynamic processes in the swash zone. The XBeach process was evaluated by developing a numerical algorithm to tackle this drawback. Six experimental tests were performed using the proposed and original XBeach models. The average morphological beach change errors of the proposed and original models were 5% and 10%, respectively. The groundwater head estimation error of the original model was 8% compare with less than 3% of the proposed model. The proposed XBeach model effectively handled the phase error of the original XBeach and stimulated the hydrodynamic and morphodynamic processes in the swash zone more accurately.