p = porosity of sediment 



For values of Y greater than 60, C , n^ , m-^ , and A have the values 

 0.025, 0, 1.5 and 0.17, respectively. 



64. The Ackers and White formulation modified for waves has been used in 

 the past to determine sediment transport within surf zone areas (e.g., Swart 

 1976, van de Graaff and van Overeem 1979, Willis 1978, and Swart and Fleming 

 1980). It would appear, however, to be questionable to assume that an 

 approach developed to determine sediment transport by current action would be 

 appropriate to handle sediment transport in an area where turbulence due to 

 wave breaking is the major mechanism for placing sediment in a state that 

 allows transport by currents. However, outside the surf zone where waves are 

 nonbreaking, the influence of waves is to increase the velocity of flow felt 

 by sediment grains. Thus it is reasonable to use in the latter region a 

 current action approach that is modified to consider also the current action 

 exerted on the bottom by waves. 



65. Swart (1976) assumed that suspended load was the main sediment 

 transported in the surf zone. Therefore, he modified the shear velocity to 

 account for waves by increasing the shear velocity as follows: 



(v*) 



waves and current 



(vj 



current 



1 + 



1/2 



(89) 



where 



h = C l (fw i /2g) 



12h 



1/2 



C = 18 log 



(90) 



(91) 



fw = Jonsson's (1966) friction factor based on bed roughness r 1 



u = wave orbital velocity 



o J 



Equation 89 was originally developed by Bijker (1967) and modified by Swart 

 (1974a). 



66. Van de Graaff and van Overeem (1979) noted that within the surf zone 

 both suspended and bed load are significant and thus concluded that Swart 's 

 approach was not correct. They proposed increasing the mean velocity of flow 

 in addition to the shear velocity by using the following equation: 



51 



