5it tan 8 , , . 1/2 . „ ... , , 



v = -r-r YC (gh) sin cos 9 (114) 



lb c 



80. Every time the wave climate is changed, a new equilibrium profile 

 (given by the W. values) must be calculated. The existing profile at this 

 particular time then becomes the initial profile used to determine the (L 2 - 

 ^l^io va l ufeS at a H points i . The rate of sediment transport (S ) is 



y it 



then determined at each point i and is modified to include the effects of 

 oblique wave attack. This rate of transport varies with time exponentially. 

 Thus, the profile begins initially to move toward an equilibrium profile at a 

 fast rate, but the rate slows as the profile approaches an equilibrium 

 profile. Actually, the time required to reach equilibrium is long compared to 

 the time a typical wave condition exists. Thus, profiles are always moving 

 toward equilibrium profiles but never fully reaching them. 

 Model testing 



81. The profile response model was compared with laboratory tests of 

 profile modification under wave attack and with prototype measurements of 

 profile modification. Figures 25 through 28 show comparisons between beach 

 profiles that were measured in experimental tests by Eagleson et al. (1963) 

 and results of the profile response model. The solid lines are profiles 

 calculated by the model, and the dashed lines are measured profiles. The only 

 parameters varied in the numerical model calculations were those that were 

 varied in the laboratory test (initial profiles, wave heights, wave periods, 

 and duration of the tests). The major features of the measured profiles are 

 reproduced in the numerical model results. The agreement between measured and 

 calculated profiles is quite remarkable considering the great complexity of 

 the fluid-sediment interaction process. 



82. Comparisons also have been made between measured profile modifica- 

 tion in the prototype and numerical model results. For example, a storm 

 during the period 16-21 February 1980 at Santa Barbara, California, was docu- 

 mented (Gable 1981) in detail during the Nearshore Sediment Transport Study 

 (NSTS). This was a large storm that produced approximately 40 m of shoreline 

 erosion. Daily profile measurements were made by the NSTS in addition to 

 complete directional spectral wave data. Figure 29 shows good agreement 

 between measured profiles and the profile response model simulation over the 

 5-day period of the storm. The only inputs to the numerical model were the 



60 



