A5/2 

 16(S - Da' W (2b) 



where 



K = dimensionless empirical coefficient (of order 0.4) 



H = significant wave height, m 

 C = wave group velocity, m/s 

 9, = angle of breaking waves to the shoreline, deg 



S = ratio of sand density to water density 



a' = volume of solids/total volume 



r = conversion factor from Root Mean Square (RMS) to significant wave 

 height, if necessary (equals 1.416) 



The subscript b indicates quantities at wave breaking. The group velocity 

 at breaking is calculated from: 



( c e Wi\V /2 



where 



g = acceleration of gravity, m/s 



Y = ratio of wave height to water depth at breaking, approximately 

 equal to 0.78 



38. The angle 8, is the angle of the breaking waves to the shore- 

 line. It is equal to the difference between the angle the breaking waves 

 makes with the x-axis and the angle the shoreline makes with the x-axis: 



e b S ■ % - tan ~ 1 (S) <"> 



where 



9 = angle of breaking waves to x-axis, deg 



39- Common lateral boundary conditions are Q = at an impermeable 

 barrier such as a long jetty or groin, and 3Q/3x =0 on a beach that has a 

 stable (fixed) shoreline position. The latter boundary condition on Q can 

 also be expressed as 3y/3t = (see Equation 1). 



40. In addition to lateral boundary conditions, which are necessary to 

 solve any problem, it is sometimes required to constrain the solution, i.e., 

 restrict movement of the shoreline position. For example, the shoreline along 



17 



