CMS-Wave (formerly known as WABED) is a 2-D wave spectral transformation (phased-averaged) model (Mase and Kitano 2000; Mase 2001; Mase et al. 2005). It is a phase-averaged model, which neglects changes in the wave phase in calculating wave and other nearshore processes from the output wave information. This class of wave models represents changes that occur only in thewave energy (action) density. Isobe (1998) and Panchang and Demirbilek (1998) have reviewed different types of wave prediction models for offshore and coastal engineering applications. Because phase-averaged energy (action) balance models neglect wave phase, they cannotdirectly predict wave diffraction and reflection caused by bathymetric features and structures. However, these effects may be incorporated in such models in approximate ways. For example, wave diffraction has been approximated in the STWAVE model as a form of diffusion (Smith et al. 1999), whereas wave reflection is omitted. Various methods have been investigated over the last 60 years to include diffraction and reflection in wave models (e.g., Penney and Price 1952; Rivero et al. 1997a, 1997b; Yu et al. 2000; and Holthuijsen et al. 2004).

The CMS-Wave model contains theoretically developed approximations for both wave diffraction and reflection and, therefore, is suitable for conducting wave simulations at coastal inlets. Successful performance of CMS-Wave has resulted in its inclusion in CIRP’s CMS. CIRP has improved model efficiency to minimize CMS-Wave run time, developed implementation of the model inside the Surface-water Modeling System (SMS), and added new capabilities to the model for calculation of wave radiation stresses for wave-induced current, and wave-generation-growth. CMS-Wave is implemented in the CMS through the (ERDC/CHL CHETN-III-73 July 2006) SMS, and input files are similar to those for the existing spectral model STWAVE (Smith et al. 1999) in the SMS.

CMS-Wave employs a forward-marching, finite-difference method to solve the wave action conservation equation. Capabilities of the model include wave shoaling, refraction, diffraction, forward reflection, depth-limited breaking, dissipation, and wave-current interaction (Mase 2001; Mase et al. 2005). Wave diffraction is implemented by adding a diffraction term derived from the parabolic wave equation to the energy-balance equation. The model operates on a coastal half-plane so primary waves can propagate only from the seaward boundary toward shore. If the seaward reflection option is activated, the model will also perform backward marching for seaward reflection after the forwarding-marching calculation is completed