where W^ is a coefficient depending on wind speed, and 9 is the 

 structure slope (6 = 90° for Galveston walls). For onshore wind speeds 

 of 60 raph or greater Wj? = 2.0 should be used. For a wind speed of 

 30 mph, yif = 0.5; when no onshore winds exist, W^ = 0. Interpolation 

 between values of Wy given for 60, 30, and mph will give values of 

 W^ for intermediate wind speeds. Equation 7-8 is unverified, but is 

 believed to give a reasonable estimate of the effects of onshore winds 

 of significant magnitude. For a wind speed of 30 raph, the correction 

 factor k' varies between 1.0 and 1.55 depending on the values of 

 (h-dg)/R and sin 6. 



Values of a and Q^ larger than those in Figures 7-23 through 7-31 

 should be used if a more conservative (higher) estimate of overtopping 

 rates is required. 



Calculation of wave overtopping rates is illustrated by the following 

 example. 



************** FXAMPLE PROBLEM *************** 



GIVEN : An impermeable structure with a smooth slope of 1 on 2.5 is 

 subjected to waves having a deepwater height H^ = 5 ft. and a 

 period T = 8 sec. The depth at the structure toe is dg = 10 ft; 



crest elevation is 5 ft. above SWL. Onshore winds of 35 mph are 

 assumed. 



FIND : Estimate the overtopping rate for the given wave. 



SOLUTION : Determine the runup for the given wave and structure. 

 Calculate, 



-T= = 2.0 , 



Hi 5 



H' 



5 



gT2 32.2 (8)2 

 From Figure 7-11, since 



i .s 2.0 , 



= 0.0024. 



— - = 2.9 (uncorrected for scale effect) 



7-49 



