Coupling Phase-Resolving Nearshore Wave Models with Phase-Averaged Spectral Wave Models in Coastal Applications

Phase-resolving wave models are best suited for the class of coastal applications with strong wave diffraction and reflection caused by coastal structures. Often, a deepwater spectral wave transformation model has to be coupled to a phase-resolving wave model to ensure accurate modeling of the local wave field near structures. This paper presents the development and evaluation of simplified methods for coupling a phase-resolving model CGWAVE with a phase-averaged model CMS-Wave. Four methods, which are, single point input, geometric mean, spatially varying wave height input, and quasi-spectral wave input, were tested at the Grays Harbor/Half Moon Bay area, a very dynamic site with complex geometry and bathymetry. Comparison of results with field data indicate that monochromatic CGWAVE solutions with a single-point wave input may not be reliable in certain applications since this method ignores the spatial variation and spectral properties of the incident waves at the open boundary. Results also indicate that directional wave spreading in the coupling of two wave models is important even for swell-like wave conditions. By combining a finite number of monochromatic CGWAVE solutions using the proposed quasi-spectral methods, the wave height estimates were improved in the Half Moon Bay as compared to data.