where 



(v) . . - (v) 



wave and current current 



1/2 



(92) 



(93) 



18 log 



/ lOh 



D 



(94) 



fw = Jonsson's friction factor with D as bed roughness 



Equation 92 was developed also by Bijker (1967) and modified by Swart (1974a). 



67. Beyond the surf zone where waves are nonbreaking, the waves do not 

 increase the level of turbulence since turbulence is confined to a narrow 

 boundary layer by the oscillating wave orbital velocities. Since the shear 

 velocity is dependent upon the intensity of turbulence and thus the total 

 energy degradation rather than the net traction on individual sediment grains , 

 the shear velocity is not changed by wave action. With the wave-induced tur- 

 bulence confined to a narrow boundary layer and the waves propagating essen- 

 tially without energy loss, the 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 according to Equation 92. How- 

 ever, the shear velocity must remain unchanged. Thus Equation 82 becomes 



with 



S = 



( r 2I 1/2 



\ J 



k ( F - ^ 



A 1 



(95) 



tlM 



L/2 1_n l 



[g(s - 1)D] 



1/2 



(^ ^ 



n^l 



(96) 



52 



