Grain Size (mm) 



Elapsed Time (hr) 



Figure 66. Effect of D on bar volume 



456. Equilibrium maximum bar height increased by percentage values 

 about half those of bar volume for the same changes in grain size. Movement 

 of the bar center of mass was only slightly affected by changes in most model 

 parameters. However, change in grain size did have a significant influence on 

 the location of the center of mass, as seen in Figure 67. Initiation of bar 

 formation occurred roughly at the same place, independent of grain size; 

 however, after initiation, bar movement was considerably greater for the finer 

 grain sizes. 



457. Grain size also influences the spatial decay coefficient for the 

 transport rate seaward of the break point (see Equation 22). The decay 

 coefficient increases with grain size, implying that the transport rate 

 decreases more rapidly, moving sand less seaward. 



Influence of wave period and height 



458. So far in the sensitivity analysis, only parameters which are 

 expected to be effectively constant for a specific beach have been inves- 

 tigated. Since the driving force in the numerical model is wave breaking, it 



190 



