change model in the preliminary study. However, the SIO gage provides a 

 weighted angle defined from components of the wave radiation stress, and not a 

 direct wave angle. Therefore, direction results must be interpreted with 

 caution. Although the distribution of incident wave angles did not compare 

 well with the other data sources, a uniform adjustment to the incident wave 

 angles was determined during the model calibration. 



WAVE TRANSFORMATION ANALYSIS 



Because the magnitude and direction of the longshore sand transport rate 

 are dependant on the sine of the breaking wave angle with respect to the shore 

 and on the breaking wave height raised to the 5/2 power, calculated shoreline 

 change is sensitive to the input wave conditions. In order to obtain accurate 

 estimates of the nearshore wave climatology, a wave transformation model is 

 required which accounts for wave refraction, diffraction, and shoaling over a 

 natural bathymetry. The numerical model, Regional Coastal Processes WAVE 

 (RCPWAVE) (Ebersole, Cialone , and Prater, 1986), was utilized to calculate the 

 propagation of representative classes of linear waves over a digitized 

 bathymetry which extended from the east jetty of Anaheim Bay to beyond the 

 Santa Ana River. RCPWAVE accounts for refraction, shoaling, and diffraction 

 caused by the underlying bathymetry and can be applied on a regional basis 

 economically. The bathymetric grid used in this study consisted of 97 cells 

 alongshore and 22 cells offshore, and grid cell dimensions were 600 ft 

 alongshore and 300 ft offshore. 



Execution of the wave transformation model for every offshore wave 

 condition would require extensive resources and would not be justified 

 considering the level of accuracy and sophistication of the data input and 

 numerical models. Therefore, another approach was taken which is commonly 

 used in regional -scale shoreline response studies performed by CERC (Kraus et 

 al . 1988). In preparatory analysis, the offshore wave data were separated 

 into seven 22.5-deg angle bands and two 12.25-deg angle bands centered about 

 the compass directions of northwest, west northwest, west, etc. An RCPWAVE 

 run was performed for wave periods from 5 sec to 21 sec in 2 -sec increments in 

 each angle band. A wave height of unity and a period corresponding to wave 

 periods existing in the offshore wave data was input at the offshore boundary 

 (at a depth approximately equal to that of the measured or predicted offshore 



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