equations) and the computer programs see Appendix D. The two values obtained 

 for the surveys of 20 April and 1 December 1976 were averaged to obtain the 

 value used in the model, A = 0.2606. Stations 101+00 through 121+00 were 

 treated separately for the purpose of obtaining values with which to initial- 

 ize those parts of the contours in the model and for comparison of the model 

 predictions with the prototype values. Note that although the breakwater 

 extends only to about Station 118+00, the influence of the structure and 

 dredging extends beyond that location and so, although arbitrary, the 121+00 

 station was chosen as the dividing line. The initial and final values of the 

 scaling parameter A for the profiles were 0.3233 and 0.3528, respectively. 

 Because the initial shoreline is so irregular, a discontinuity between 121+00 

 and 122+00 is not evident. 



One further idealization was made. The jetty-breakwater system was 

 idealized as shown in Figure 19. This was required to simplify the physical 

 situation, and although waves, currents, and sediment do pass through the 

 opening in the prototype, it is hoped that they are of secondary importance. 



The results of the numerical modeling of Channel Islands Harbor are 

 presented in Figures 20 and 21. The first figure presents the shoreline 

 contour (depth = 0); the second figure presents the farthest offshore, 

 modeled contour. In both cases, the initial shoreline represents the model 

 and prototype (after fitting of the profiles). The initial shoreline contour 

 is further offshore along the section of beach beyond the end of the 

 breakwater, while in the lee of the breakwater, as would be expected after 

 dredging, the shoreline is closer to the base line. The final prototype 

 contour has undergone erosion along the reach beyond the tip of the 

 structure, and accretion in the lee. 



The model's shoreline contour has undergone similar changes, and on the 

 average, represents the final prototype contour quite well. The JMA)Ct!l 

 contour has been displaced quite similarly to the shoreline contour with 

 shoreward movement (erosion) along the reach beyond the tip of the breakwater 

 and seaward movement (accretion) within. It appears that the final model's 

 shoreline has predicted too much erosion and not enough accretion. Several 

 parameters could be incorrect, with the onshore-offshore sediment transport 

 rate coefficient, CqfF' perhaps the most likely. Overall, the model seemed 

 to predict reasonable values of the contours. 



V. SUMMARY AND RECOMMENDATIONS 



Some of the parameters that the model does not include are important and 

 should be mentioned. As stated previously, the model does not include bar 

 formation. This is precluded by an n-line system. There are no provisions 

 for water level fluctuations or currents. Improvement to the model could 

 also be facilitated with better longshore and cross-shore sediment transport 

 relationships. A more reliable equation for distribution of sediment 

 transport across the surf zone would also be helpful (or further testing and 

 calibration of the equation proposed herein). Finally, combining refraction 

 and diffraction using equations to predict their combined effect would 

 improve the wave field. The program was constructed such that improvement 



48 



