10 



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F==l 



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F=l 



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. frH=o-oi4 



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y 



y 



y 



















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 ■ 





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 1 



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4k10 



10' 



Hb/gT 



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Figure 9. Criterion for distinguishing profile type by use of 

 ratio of breaking wave height and grain size, and Ursell 

 number at breaking 



speed is superior to the grain size in development of profile classifications, 

 as it incorporates both grain shape and fluid viscosity (water temperature). 



218. An attempt was made to incorporate initial beach slope in the 

 criteria for bar /berm profile classification using the LWT data set, but 

 addition of this parameter did not increase predictability. In practice, 

 determination of a representative beach slope on an irregular profile intro- 

 duces some ambiguity, and a transitional slope would not be known in a 

 predictive field application. A representative beach slope is implicitly 

 contained in the fall speed (or grain size) because the equilibrium beach 

 profile depends on this quantity (Moore 1982, Dean 1987). This implies that 

 the existing beach profile should not be far from equilibrium for Equations 

 2-6 to be applicable, a condition expected to be satisfied at locations on the 

 open coast and far from structures such as large jetties. 



219. In the present study, use of the dimensionless fall speed as the 

 sediment-related parameter gave a good delineation between bar/berm profiles, 

 and this parameter has a sound physical basis, as first explained by Gourlay 



70 



