3^y, 9/2 



9x 



Adding both equations yields: 



,2 

 q 3 y 



D ^ 2 



9x 



+ 



d2 



in which 







) 



^2 \ 3^(^1 " ^2] _ 9y 



D. / .2 3t 

 3x 



(36) 



a = ^^ and y = i (D^y^ . D^y^) . (37) 



^1 "^2 

 For simplicity, Bakker (1968b) assumes ■=— = y-— , which implies that 



1 2 



derivatives of the littoral drift transport with respect to 



are proportional to depth D . Then, dividing 



dQ 

 da 



equation (6) by D and D respectively, and subtracting, yield : 



D ~ir ' DTdT ^^*^ " ~9t ^^^^ 



9x 12 



where y^ = y, - y^ , which is the equation for the offshore-onshore 

 transport q y^ . It is interesting that the offshore-onshore transport 

 is independent of the longshore transport. 



Using the auxiliary variable. 



36 



