Elapsed Time (hr) 



Figure 65. Effect of T on bar volume 



and size of the bar, which is more pronounced for finer material. A smaller 

 value of D , occurring for finer grain sizes, corresponds to a flatter 

 equilibrium beach profile, thus requiring more sand to be moved before 

 equilibrium is attained. 



454. Sensitivity of model predictions on grain size was investigated. 

 Since equilibrium energy dissipation decreases rapidly with grain size (Moore 

 1982), bar volume correspondingly increases, as illustrated in Figure 66. 

 (Values of D^^ used to obtain the curves in Figure 66 are 0.75 the value of 

 those obtained by Moore (1982), according to the results of the model calibra- 

 tion in Part VI. ) 



455. Changing the median grain size from 0.50 to 0.40 mm increased the 

 equilibrium bar volume by about 20 percent, whereas a decrease in median grain 

 size from 0.40 to 0.30 mm gave an increase of about 90 percent. Corresponding 

 changes in values of D^^ were 10 percent and 70 percent, respectively. 

 Changes in maximum bar height were also significant as the grain size was 

 decreased, although not as great as for bar volume. 



189 



