where V is the quantity of water overtopping the wall in cubic meters 

 per meter or cubic feet per foot length of wall, h s the wave height at 

 the shoreline in meters or feet, 

 and 



hjj the wall height in meters or feet, 



ho 



(322) 



where R would be the vertical height of wave runup on a similar wall 

 high enough to prevent overtopping. 



Wiegel (1970) gives the following empirical equation for overtopping 

 volume in cubic meters per meter length of wall 



V = 0.287 



fVh C os^-hV /2 

 Jt l \ 2 s T w/ 



dt 



(323) 



where h s is the total wave height in meters (crest-to-trough) of the 

 wave at the shoreline, T the wave period, t} the point in time where 

 overtopping begins, and t 2 the time when overtopping ends. As the 

 wall height, h^, is measured in meters from the sea level at the time 

 the tsunami occurs, it varies but its lowest value (i.e., the greatest 

 overtopping) would occur when the sea level is at the highest tidal stage 

 Values for overtopping are shown in Figure 55 . 



0.2 0.3 0.4 0.6 8 1.0 2 3 4 6 6 10 



Elevation of Tsunami Crest above Seowall, (m) 



Figure 55. Overtopping volumes 



(after Wiegel, 1970) . 



161 



