a and 3 are empirical coefficients that depend on the structure's charac- 

 teristics. Equation (11) is valid for the condition 



when 



-(a + 3) 



h - d_ 



< & < (a - 3) 



H i 



(h - d g ) 



H i 



H f 

 < -(a + 3) , — = 1.0 



H i 



(h - d s ) 

 H i 



H t 

 > (a - 3) , — = 



H i 



when 



For a thin vertical wall, a = 1.8 and 3 = 0.1, values which apply to a thin 

 sheet-pile weir section. For a vertical-side breakwater with its breadth 

 approximately equal to the water depth, a = 2.2 and 3 = 0.4. For rubble 

 structures where transmission is by overtopping only, the transmission coeffi- 

 cient, H t /H jL is (Seelig, 1980) 



-£- = I 0.51 - 0.11 -j fl M (12) 



where B is the crest width of the structure, and R the wave runup height 

 above the Stillwater level (SWL) that would occur if the structure crest were 

 above the limit of runup. For a rubble structure, the runup is given by 

 Ahrens and McCartney (1975) as 



R=( ^ )Hl (13a) 



\l + bt/ i 



where 



5 = surf parameter given by. 



tan 

 K = , — (13b) 



a, b = empirical coefficients equal to Q.692 and 0.504, respectively, 

 for a structure with two layers of rubble armor 



= angle the seaward face of the weir section makes with a 

 horizontal 



L = the deepwater wavelength given by L Q = gT 2 /2ii with T the 

 incident wave period and g the acceleration of gravity 



When transmission is both through and over the rubble structure, H^/H^ is 

 given by Seelig (1979) as 



^ = / K 2 + K| (14) 



where K is a transmission coefficient for wave energy transmitted by over- 

 topping and K t a transmission coefficient for wave energy propagated through 

 the structure. 



36 



