0.5 1 1.5 2 



ALONGSHORE DISTANCE (x/L) 



Figure 29. Shoreline evolution updrift of a groin which is 

 totally blocking the transport of sand alongshore 



For a specified amplitude of the sand transport rate and the depth of closure, 

 the ratio of shoreline positions at a given point for two different incident 

 breaking wave angles is proportional to the following ratio of respective 

 tangents of the angles: 



tan a 



ol 



tan a 



(65) 



o2 



64. Equation 64 is valid only until the shoreline has reached the tip 

 of the groin, after which time bypassing of sand is assumed to take place. 

 This bypassing happens when y = L (length of the groin) at x = , which 

 occurs at time t„ : 



t G e . . 2 



4 tan a 



(66) 



48 



