Numerical Modeling of Swash Zone Morphological Processes in Coarse-Grained Beaches with XBeach Open-Source Model

Document Type : Article

Authors

1 PhD candidate of Shahrood University of Technology

2 Faculty of Coasts, Ports and Marine Structures, Civil Engineering Department, Shahrood University of Technology, shahrood, Iran

3 Faculty member of Shahrood University of Technology

Abstract

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. In this regard, evaluating the performance of the XBeach model based on the SB and NH modules, comparing the results of morphological process simulations, and sensitivity analysis of the results under different coastal conditions have been considered as research gaps in this field. Based on this, this research is dedicated to modeling three different laboratory models from Masselink, 2012 Zanden,2016 and Demirbilek, 2007 with varying hydrodynamic-morphodynamic conditions to evaluate the performance of the XBeach model in simulating morphological processes of coarse-grained beaches with the presence of bed porosity effects in the form of infiltration/exfiltration. In the numerical modeling process, after calibrating and sensitivity testing the models, the results are extracted and compared with laboratory models. The results of this research indicate that the XBeach model has an acceptable performance in modeling hydrodynamic and morphodynamic processes in the Swash region, and simulation with the NH module performs better compared to the SB module (with a reduction in modeling error of over 5% in various models). Additionally, the results show that phase errors during water infiltration/percolation into the aquifer in XBeach lead to the expansion of numerical modeling errors in calculating changes in the seabed profile and aquifer water level. Despite substantial advances, XBeach remains yet to be further developed since it is inefficient in modeling interactions between the aquifer level and seawater. Those studies should aime 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.

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