The reflection coefficient, and consequently clapotis height and wave 

 force, depends on the geometry and roughness of the reflecting wall and 

 possibly on wave steepness and the "wave height-to-water depth" ratio. 

 Domzig (1955), and Greslou and Mahe (1954), have shown that the reflection 

 coefficient decreases with both increasing wave steepness and "wave height- 

 to-water-depth" ratio. Goda and Abe (1968) indicate that for reflection 

 from smooth vertical walls this effect may be due to measurement tech- 

 niques, and could be only an apparent effect. Until additional research 

 is available, it should be assumed that smooth vertical walls completely 

 reflect incident waves and x - ^' Where wales, tiebacks or other struc- 

 tural elements increase the surface rougliness of the wall by retarding 

 vertical motion of the water, a lower value of x may be used. A lower 

 value of X also may be assumed when the wall is built on a rubble base 

 or when rubble has been placed seaward of the structure toe. Any value 

 of X less than 0. 9 should not be used for design purposes. 



Pressure distributions of the crest and trough of a clapotis at a 

 vertical wall are shown in Figure 7-64. When the crest is at the wall, 

 pressure increases from zero at the free water surface to wd + pi at 

 the bottom, where p^ is given as 



1+X 



wH, 



cosh (27rd/L) 



(7-68) 



Crest of Clopotis ot Woll 



Trough of Clopofis ot Woll 



TTTTTTi 



Figure 7-64. Pressure Distributions - Nonbreaking Waves 



7-129 



