where the coefficient A , called the "shape parameter," determines the steep- 
ness of the offshore profile. This form of the equilibrium profile was first 
advocated by Bruun (1954) and has subsequently been shown by others (e.g., 
Dean 1977, Hughes 1978, Moore 1982) to adequately represent the shape of 
natural offshore profiles. Since steepness is a function of grain size, the 
value of A can be related to the grain diameter, although the recommended 
practice is to select an A-value which produces an optimized representation of 
the existing (pre-storm) profile. If pre-storm conditions are not known, the 
grain size diameter relationship shown in Figure 22 (Moore 1982) can be used 
to estimate an A-value. Comparisons of calculated equilibrium profiles and 
measured profiles at various project sites are given in Appendix D. 
134. One apparent disadvantage of this schematization concept is that 
certain features, such as offshore bars, troughs, navigational channels, or 
other abrupt irregularities, cannot be represented. Conversely, since the 
primary purpose of the model is to approximate subaerial beach erosion, an 
advantage of the model is that detailed bathymetric information is not re- 
quired for obtaining reliable estimates. An additional advantage is that the 
0.1 1.0 10 100 
SEDIMENT DIAMETER (MM) 
Figure 22. Shape parameter, A , versus sediment 
diameter (after Moore 1982) 
68 
