total local depth, which is the sum of h , ^ , and ^ , was also updated. 

 The total velocity components u and v„ were adjusted on the basis of sim- 

 ple continuity to account for the change in bed elevation of the cell. It was 

 observed from running the sediment transport model that model results in terms 

 of erosion/deposition rates (ft/year) along the channel became approximately 

 constant after the model was run for 150 to 180 prototype days. There were 

 minor variations from run to run as the total time was increased, but the 

 trends and magnitudes stabilized. Therefore, the above sequence was performed 

 for 180 instead of 365 prototype days to compare with field data for 

 verification. 



111. Results. Based on the trends exhibited by the prototype data, the 

 reach of the channel between sta -80+00 and sta 325+00 was divided into 

 seven zones for verification (Figure 21). A similar approach was used for 

 Model A verification. Four to six computational grid cells were in each zone. 

 The value assigned to a zone is the average of the values for the cells in the 

 zone. A comparison of the prototype average erosion/deposition rates with 

 results of Model B is shown by zones in Figure 22. Also shown in the figure 

 are prototype extrema based on 1 year of prototype data. Model B results show 

 the same trends as the prototype average results and are in approximate 

 quantitative agreement in zones 1-4 (between sta -80+00 and sta 241+56) . It 

 is not surprising that they do not match quite as well between sta 241+56 and 

 sta 325+00. This is a highly dynamic region, especially outside the jetty 

 tips (sta 251+00) and is very much dependent on the actual (rather than aver- 

 age) wave climate that existed between surveys. This can be seen in the large 

 spread between prototype extrema. There is movement of material from the off- 

 shore bar and shoals into the channel. As was pointed out previously, proto- 

 type data of 1 year's duration are not necessarily representative of a 20-year 

 average. On the whole. Model B results are reasonable and in agreement with 

 field data. 



Base tests 



112. The only difference in the bathymetries used at the start of veri- 

 fication and base tests was in the navigation channel. The sediment model 

 used the channel bathymetry from the CESAJ survey of June 1982 for the base 

 tests because the same bathymetry was used in all the other models for base 

 condition. 



63 



