wide, submerged, impermeable breakwater. His equation for the trans- 

 mission coefficient, ratio of transmitted wave height to incident wave 

 height Ht/H-i^ is given by 



H. 



1 



'1 + 



0.25 d^ 

 d -h 



0.25 ds- 0.25 hV 



"27rb / 



v/grU 



(7-9) 



where ds is the depth below the SWL at the structure toe, h is the 

 height of the structure above bottom, b is crest width, g is acceler- 

 ation of gravity, and T is wave period. The development of Equation 

 7-9 does not consider energy dissipation, and therefore does not consider 

 waves breaking on the structure or energy loss by friction. In addition, 

 the equation is valid only for shallow-water waves when d/gT^ <^ 0.00155, 

 and should not be used when h/d > 0.8. When crest width is small relative 

 to structure height (say b/h <_ 0.5) the value of H^/H^ given by the 

 equation may be too large. 



Fuchs (1951) presented an equation for calculating wave transmission 

 over a rigid, thin vertical barrier by considering power transmission 

 across the barrier. The equation is based on linear wave theory, and 

 cannot be used when transmission is by overtopping. Fuchs' equation is 



^= n- 



H, 



(47rh/L) + sinh(47rh/L) 

 5inh (47rd^^\ + (47rd^|L\ ' 



(7-10) 



and is assumed valid in water of any depth, provided the wavelength L 

 corresponds to the depth dg. In shallow water. Equation 7-10 reduces to 



for 



1 - 



(7-11) 



gT^ 



< 0.00155 , 



and in deep water Equation 7-10 reduces to 



for 



For 0.00155 < d /gT^ < 0.0793 Equation 7-10 must be used. 



(7-12) 



7-53 



