where H is the wave height, Cg is the wave group velocity, and a is the 

 angle the wave crest makes with the shoreline. Usually the breaking 

 wave characteristics (H^ , Cg^, and a^) are used to represent the wave 

 energy flux entering the surf zone. 



Each wave type was refracted toward shore by the refraction model. 

 The breaking wave values of H b , C , and approach angle, ct b were deter- 

 mined at each breaking wave-ray location, and then interpolated at beach 

 stations every 250 meters along the study area. The shoreline (plan) 

 angle at each of these 250-meter locations was measured from aerial 

 photos and the value of a then determined. The longshore component of 

 wave energy flux at breaking was calculated using equation (9) at each 

 250-meter beach station, and was then multiplied by that wave type's 

 percent occurrence. A positive value of Pj^ represented a component 

 of wave energy flux in a southerly direction and a negative value 

 represented a component in the northerly direction. 



As each wave type was refracted toward shore, and the longshore 

 component of wave energy flux was calculated, the percent contribution 

 to either the northerly or southerly components of the annual longshore 

 flux was summed, by direction, with the contribution from the other wave 

 types. The resulting totals at each 250-meter beach station represent 

 the northerly and southerly longshore components of the annual wave 

 energy flux. 



The spatial variation of these totals was significant, and the 

 sudden changes in magnitude were not representative of the actual energy 

 flux conditions. Several factors which contributed to this problem 

 were: 



(a) The refraction model used a static representation of shoreline 

 conditions and bathymetry. As soon as a concentration of wave 

 energy in shallow water occurs in the prototype, erosion 

 results and bathymetry changes to reduce the energy concen- 

 tration; i.e., nature tends to smooth out sudden changes in 

 concentrations of wave energy, but the model cannot. 



(b) The resolution of the computational grid cells close to the 

 beach were not fine enough to allow for the rapid changes in 

 bathymetry and beach planform. 



(c) The energy flux values are proportional to the product of the 

 sine and cosine values of the wave approach angle relative to 

 the beach shoreline. Consequently, subtle errors in offshore 

 angles can result in significant errors in the energy flux 

 computation at the beach face. 



(d) Diffraction effects and the influence of tidal currents were 

 not included. 



72 



