following which the force remained approximately constant or diminished 



slightly. The effective height of run-up d on the wall (Fig. D-1) showed 



2 



approximate linear relationship to u / 2g, as might be expected, yielding 



2 

 d / (u /Zg) values of about 2. for a wet bottom and 1. 5 for a drv bed in 

 w s ■' 



front of the surge. The peak pressure occurred, apparently, when this 



run-up collapsed on the reflecting bore, which formed at that moment and 



moved away from the wall. The fairly quiet water left behind exerted 



effectively only hydrostatic pressure against the wall. 



For the case of a fairly flat surge, we may take d ~ d ; C^ — 1 

 •^ ° •' t s F 



and apply to Eq. (D-24) the observation that 



1. 5 to 2.0 (D-25) 



2 

 u 

 s 



2? 



and the earlier conclusion of Eq. (D-17) with K = 1. 5 to 2. 0. Eq. (D-24) 

 then reduces to the simplified form 



F ^ 7 /ogdg (D-26) 



which is quite similar to a result obtained by Wiegel (1967) by this type 

 of reasoning. It must be noted that if d exceeds the height of the v/all 

 or structure, due allowance would have to be made for the overtopping flow, 

 which would reduce the numerical coefficient in Eq. (D-26). The latter, 

 otherwise, says that the dynamic force per unit length on a wall-type 

 structure is about 14 times the hydrostatic force from a tsunami surge. 



D-12 



