X - BEACH MODEL

XBeach is an open-source numerical model which is originally developed to simulate hydrodynamic and morphodynamic processes and impacts on sandy coasts with a domain size of kilometers and on the time scale of storms. Since then, the model has been applied to other types of coasts and purposes.

The model includes the hydrodynamic processes of short wave transformation (refraction, shoaling and breaking), long wave (infragravity wave) transformation (generation, propagation and dissipation), wave-induced setup and unsteady currents, as well as overwash and inundation. The morphodynamic processes include bed load and suspended sediment transport, dune face avalanching, bed update and breaching. Effects of vegetation and of hard structures have been included. The model has been validated with a series of analytical, laboratory and field test cases using a standard set of parameter settings. 

XBeach has two modes: a hydrostatic and a non-hydrostatic mode. In the hydrostatic mode, the short wave amplitude variation is solved separately from the long waves, currents and morphological change. This saves considerable computational time, with the expense that the phase of the short waves is not simulated. A more complete model is the non-hydrostatic model which solves all processes including short wave motions, but with more computational demand.  

The original application (surfbeat mode), funded by the U.S. Corps of Engineers in the framework of the Morphos project and the U.S. Geological Survey, was to be able to assess hurricane impacts on sandy beaches. Since then with funding from the Dutch Public Works Department, the model has been extended, applied and validated for storm impacts on dune and urbanized coasts for the purpose of dune safety assessments. With support from the European Commission XBeach has been validated on a number of dissipative and reflective beaches bordering all regional seas in the EU. 

Beyond sandy coasts, the model has been applied to coral fringing and atoll reefs, in cooperation with and with funding by the University of Western Australia, the USGS and the Asian Development Bank. The model now also includes vegetative damping effects, with support of the U.S. Office of Naval Research.

The non-hydrostatic model has been developed initially by the TU Delft (as a prototype version of the SWASH (Zijlema et al. 2011) model). For the purpose of simulating the morphodynamic processes on gravel beaches, the model was extended and validated with support from the University of Plymouth. In this mode, ship-induced waves can be simulated as well, demonstrating the flight that the model has taken since its first inception.

This development of XBeach could not have been possible without all of the above mentioned funding agencies and partners. It would also not have been possible without the enthusiastic, critical and constructive approach of all consultants, researchers, M.Sc. and Ph.D. students who have taken up XBeach, and made it into the tool that it is today.

This manual serves as an introduction to the model and a reference guide to its many functionalities, options and parameters. We sincerely hope that this document will help existing and new researchers apply the model for their purposes and advance our knowledge of coastal hydro- and morphodynamics.