Online coupling of SWAN and SWASH for nearshore applications

An online, one-way coupling procedure between the SWAN phase-averaged, spectral wave model and the SWASH time domain, multi-layered non-hydrostatic model has been developed, with the aim of modeling, seamlessly and efficiently, the wave evolution from generation to runup and land inundation. Both models can be run either on Cartesian or curvilinear structured grids with different spatial resolution, with the SWAN domain being typically larger than the SWASH domain. The coupling is obtained forcing the open offshore and lateral boundaries of the SWASH domain by directional random wave fields generated through the embedded wavemaker algorithm included in the SWASH code, based on the action density spectra computed by SWAN. This assures the continuity of the information, while preventing spurious reflection of outgoing waves. The coupling has been evaluated through comparison with laboratory data, with special attention paid to the location of the inner boundary between the two models.