243. Equation 9 is an inferior predictor of equilibrium bar volume 

 compared with the original regression equation (r^ decreased from 75 to 70 

 percent) formed by dimensional variables, since the least-square estimate will 

 be more influenced by wave period which was found to be less important for 

 determining equilibrium bar volume than wave height and sand fall speed. 

 Thus, the advantage of nondimensional quantities is gained somewhat at the 

 expense of predictability but will give a more general and physically-based 

 relationship. Figure 16 displays a comparison between the predicted equilib- 

 rium volume according to Equation 9 and equilibrium volumes extrapolated from 

 the measurements with Equation 7. 



n 



E 



ro 



E^ 



Vm (mVm) 



Figure 16. Measured equilibrium bar volume V^ and 

 empirical prediction V 



244. The temporal rate coefficient a in Equation 7 controls the speed 

 at which equilibrium bar volume is attained. Correlation between a and wave 

 and beach profile properties was in general low (correlation coefficients less 

 than 0.5). Qualitatively, a increased with fall speed (or grain size) and 

 decreased with wave height and wave period. A large a-value produces a rapid 



85 



