schemes used, if a boundary point is being computed, either a forward- 

 difference or a backward-difference of equation (39) is used (after 

 Abbott, 1979): 



Backward: y. . = (T)y. . . + (1 - i)y. . (40a) 



Forward: y. . = (T)y. , . + (1 - T)y. . (40b) 



1,J T''i,J IjJ 



IV. SIMULATIONS AND VERIFICATION 



Several simulations were run; two were attempts at verifying the 

 numerical model, the others were run to gain insight. Because a complete 

 data set does not exist, only the available data are compared. The first 

 modeling effort was to simulate the physical model tests of Savage (1959). A 

 second set of cases was run for shore-perpendicular structures. Next, an 

 effort was made to model sediment transport in the vicinity of a hypothetical 

 dredge disposal site in the 11- to 14-foot depths off Oregon Inlet. Finally, 

 the Channel Islands Harbor Longshore Transport Study (Bruno, et al . , 1981) 

 was modeled. Bathymetric changes were closely monitored during this study; 

 however, the wave climate (H, e, T) used was determined from the Littoral 

 Environmental Observation (LEO) data and uncertainties exist as to the 

 accuracy of the data. 



1. Simulation of Savage's Physical Model Tests . 



The numerical model was used to simulate one of the physical model tests 

 of Savage (1959). Test 5-57 was simulated numerically for a 10-hour period. 

 In this physical model, the mean sediment size was 0.22 millimeters, the wave 

 height averaged 0.25 feet, the wave period was 1.5 second, the wave angle was 

 30° (at a depth of 2.3 feet), and the groin was approximately 9.5 feet from 

 still water to its seaward limit. Cqff was held constant at IQ-^ feet 

 per second throughout the profile for this simulation. The offshore profile 

 is presented in Savage (1959). Figure 6 represents three of the eight 

 contours simulated. Note that the initial 0.3- and 0.5-foot-depth contours, 

 in the numerical representation are too far seaward by approximately 2 feet. 

 This is due to the h = Ay2/3 equation as compared to the equilibrium 

 physical model profile. Realizing this, it is the shape of the contour which 

 must be used as an indication of the numerical model predictions. The 

 general trend of the contours is similar, although the numerical model 

 contours are displaced farther seaward as expected. The major differences 

 are in the diffraction zone. 



2. Several Runs Using Shore Perpendicular Structures to Demonstrate Effects 

 of Altering Some of the Pertinent Parameters . 



In the following simulations, the models were run until their 

 near-equilibrium values were achieved. Coefficient Cqff was not a function 

 of depth (beyond the surf zone) but was held constant throughout the 

 simulated area. Important variables are as shown in the figures. Only one 

 wave condition (Hq = 3 feet, T = 7 seconds, and a deepwater wave angle uq 



28 



