phenomenology of interaction between wave and shoreline is not accurately 

 defined mathematically. 



2. Example of Shoreline Evolution . 



Because of its importance, an example application of the theory of 

 shoreline evolution is presented. However, the example is slightly 

 modified to account for the generally accepted longshore transport rate 

 formula: 



Q = ^ Pg H^ Cg sin 2a^ , (24) 



where 



Q = longshore transport rate cubic feet per second 



a, = wave breaking angle 



H = breaking wave height 



C = wave group velocity at breaking 



-3 

 k = a constant - 6.42 x 10 



pg = specific weight of seawater. 



For the case of a groin perpendicular to shore, consider the average 

 beach conditions: 



H, = 5 feet 

 b 



d^ = 6.4 feet 



c ° 



a = 5 

 o 



D = 20 feet 



C = \/ gd, = 14.4 feet per second 

 g b 



Thus, 



^= ^ I6 Pg "b S ^°" ^\ 



_ (6.42 x 10"^) (64) 5" [14.4) ^ 



8 x 20 "-^^ ■ 



Substituting into equation (10), yields: 



30 



