GROIN 





Figure 28. Definition sketch for the case of a groin 



62. A groin interrupts the transport of sand alongshore, causing an 

 accumulation at the updrift side and erosion at the downdrift side. The solu- 

 tion describing the accumulation part is 



y(x,t) = 2 tan a /et ierfc 



2/ e t 



(63) 



for t > and x > 



The solution can also be written as follows: 



y(x,t) = 2 tan a 



et -x Met 



- 2 erfc 



2/eT 



(64) 



This expression is obtained by integrating the function ierfc by parts. A 

 nondimensional plot of the shoreline evolution updrift of a groin is shown in 

 Figure 29. 



63. The shoreline position has been normalized with a characteristic 

 length (the groin length) and the tangent of the incident breaking wave angle. 



47 



