X. = 



6(s ). 



y i 



6 t So- 

 li 2i 



(107) 



Yo - y 



LI = W i" [ L 2-\ 

 io \ / 10 



bi 



(108) 



(109) 



Subscript m refers to middepth (6... = 0.56) , and subscript o refers to 

 time t = . W,_ is the difference in length between the transition distance 

 for an equilibrium profile and the transition distance for an initial profile 

 (Figure 24) . 



79. Although the Swart model is a two-dimensional onshore-offshore 

 model, transport depends upon the angle at which waves attack the D-profile 

 area. Oblique wave attack produces increased shear stress on the bed due to 

 the presence of near shore currents generated by the oblique wave attack. 

 Swart found that ( s v )-; increases when the three-dimensional effect of 

 oblique wave attack is included. The increase is given by the following 

 factor: 



"|4.5 



where 



N, 



1 + m 



2 \ 5 T U o 



\ Jo, 



m = 1.94 + 2.97 sin 

 3 b 

 5 



= angle of wave incidence at breaking 



1/2 

 J 



c h (t' 



(110) 



(111) 



(112) 



Cv = Chezy coefficient 



fw = wave friction factor (Jonsson 1966) 



u = wave orbital velocity at the bed 



Nr 



1.27 - 0.39 sin 



(113) 



The longshore current velocity v is computed using the following expression 



59 



