concerns related to the suitability of the hindcast data set in shallow waters, the approach used to compute the total theoretical resource from the maps of wave power density, the technology assumptions utilized for assessment of the total technical resource, and the lack of a demonstrated GIS tool. These concerns are discussed more fully below.
At a resolution of 4 ft, the WAVEWATCH III simulations cannot capture wave transformation effects due to bathymetric features over shorter spatial scales because the simulations cannot resolve such variability. Yet, these bathymetric effects are known to be important at depths shallower than approximately 50 m (∼160 ft) (Komar, 1998). It is important to note that these shallow-water regions may be areas of significant interest to developers of wave-energy-extraction devices. The methodology used precludes providing site-specific information to such developers. Reliable site-specific information in shallow waters can only be produced using results from models with higher spatial resolution that include the consideration of shallow-water physics. The wave resource assessment group acknowledges that its results will not be accurate in the shallower waters of the inner continental shelf, and it states that the shallowest water depths that the group intends to analyze are 50 m (going down to 20 m on the Atlantic coast, where the continental shelf is smoother and less steep). Yet, figures and tables that include results for shallow depths have been repeatedly presented in the materials of the group. Reporting such values is highly misleading and should be avoided.
The wave power density at a given location is estimated by the wave resource assessment group using the concept of wave energy flux impinging on unit diameter cylinders from any direction. The use of the unit cylinder concept results in the loss of the directional information contained in the WAVEWATCH III hindcast database. A consequence of this omission is the consideration only of the magnitude of the vector quantity of wave power density. An example of the potential misinterpretation of the resulting nondirectional (scalar) power density can be illustrated by considering a case of straight-and-parallel depth contours. In this case, the conservation of wave energy flux dictates that the shoreward component of wave power density remains constant across the continental shelf. In addition, wave refraction causes a general decrease in the angle of incidence of the waves, resulting in wave power vectors that are closer to being perpendicular to bathymetric contours as the waves travel toward the shore. The combination of these two processes causes an apparent reduction of the scalar wave power estimate as defined here, even in the absence of any dissipative process (such as bottom friction), despite the fact that the shoreward component of the associated vector will remain unchanged.
The lack of directional information in the wave power density maps also represents a bias toward nondirectional technologies, such as a point