0- 



t ' = -2_ — 













-0.3- 









-0.6- 



'j5— "^"^"^ 







-0.9- 



\ : %^^^^'^ 



'-¥ 





-1.2- 









-1.5- 



1 — j— ...... ... 



I 1 - 



1 



0.5 1 1.5 2 



ALONGSHORE DISTANCE (x/L) 

 Figure 30. Shoreline evolution downdrift of a groin with 



_Yt 



bypassing described by Qt,(1 - e ) (Q D /Q = 0.7 , 



a „ a o 



a. = 0.4 rad , yL It = 2) 



bypassing sand discharge will equal the transport rate alongshore behind the 

 groin at equilibrium conditions. Consequently, the initially eroded area 

 downdrift of the groin will fill when the bypassing sand rate reaches its 

 maximum, and the beach will become straight again. 



71. In order to investigate the effects of the linearization of the 

 governing equation (Equation 9) on the solution for a groin, numerical simula- 

 tions were carried out with the original sand transport equation (Equation 7). 

 Selected results are displayed in Figures 31 and 32. From the two figures it 

 is seen that the linearization procedure degrades the solution if the incident 

 breaking wave angle is about 30 deg. However, the analytical solution has 

 surprising accuracy, considering the approximations made. 



51 



