(d) the effects of a (skewness) and S (shape) are mostly dismissed 

 but it is generally stated that they should be the same in model and 

 prototype; and 



(e) u/W is often neglected because it can be argued that W is 

 already included in the sediment characteristics and u is included in 

 the wave characteristics. 



The investigators generally concur with points (a) and (b) . The 

 initial slope, ioj is shown later in this report to be important if it 

 is made too steep. A major part of this study has been devoted to the 

 effects of a^ and S on equilibrium profiles. Paul, Kamphuis, and Brebner 

 (1972) incorporated the effects of D50, o^, and a by defining an equiva- 

 lent sediment diameter which included these effects. It seems unlikely 

 that such an assumption will always be valid. 



Monroe (1969) performed a series of tests comparing a rounded sand 

 (oolite) and an angular quartz sand and found little difference in profile 

 shapes . 



Although the applicable fall velocity is often considered as that 

 obtained in still water, the phenomenon in the breaker zone is inherently 

 turbulent in character; Murray (1970) showed that the true fall velocity 

 of very lightweight material can be as much as 30 percent less when 

 measured in a turbulent medium. Since the physical properties of the 

 sediment are directly 'available, the fall velocity of a sediment particle 

 in the breaker zone has not been reliably established and discretion is 

 necessary in the use of relationships for this parameter obtained under 

 very different flow conditions. 



In view of the disadvantages and use of questionable approximations 

 which are inherent in the dimensional analysis approach, a purely 

 empirical approach based on attempts to match gross beach profile measure- 

 ments, was proposed by Noda (1972). 



4. Empirical Modeling Law Based on Beach Profile Similarity . 



Noda (1971, 1972) developed a model law based on an empirical fitting 

 of the beach discontinuity distance, 3 (see Fig. 1). 



The basic model requirement is to relate a model sediment density and 

 grain size to the geometric-scale ratios. This is assumed in the form: 



n^ = fi (A,y) = xV , (15) 



and 



n = f2(A,y) = xV . (16) 



M. 



