y 2 (x,t) = 



ol r 2 o2 



(91) 



for t > and x > . 



The quantity a represents a mean diffracted wave angle behind the seawall. 

 The solution in nondimensional form is presented in Figure 40 (expressed in 

 terms of the coastal constant e i)- 



-2 -1.5 -1 -0.5 0.5 1 

 ALONGSHORE DISTANCE (x/L) 



Figure 40. Shoreline evolution in the vicinity of a seawall 



where erosion and flanking may occur behind it (a =0.2 rad , 



a „ = 0.4 rad , 6 = 0.6) ' ! 

 o2 



82. A characteristic length L is chosen to normalize the shoreline 



position. In Figure 40 the time has been normalized by use of the quantity 



L 2 /e l . 



Shoreline Change at a Jetty, Including Diffraction 



83. In the shadow zone of a long groin or jetty, it may be an 



63 



