effect of waves is to increase the traction on individual grains by increasing 

 the mean velocity felt by the grains. Thus the mean velocity of flow must be 

 increased, but the shear velocity must remain unchanged. The mean velocity of 

 flow is increased by using the following equation developed by Bijker (1967) 

 and modified by Swart (1974): 



wave and current current 



1 + i 1^2 -^ 



1/2 



(73) 



where 



/fw^ 

 ^2 - SV2g 



1/2 



(74) 



C„ = 18 log 



(^) 



(75) 



fw„ = Jonsson's (1966) friction factor with D as bed roughness 



u = wave orbital velocity 

 o 



Thus Equation 66 becomes 



q = 



1 - p 



11/2 \"1 



1 + 2 V^2 - 



r 1 



-^ (F - A) ^ 



(76) 



with 



F = 



ll/2/^~"l 



} "■ 2 1^2 -. 



^2^)1 i v/-(/^XoS^)"^"^ 



[g(s - 1)D] 



1/2 



(77) 



41 



