and 



h - d 



0.471 



R 



gives a monochromatic overtopping rate of 



Q^ = 2.963 cubic feet per second per foot . 



Using Table 1 for a = 0.08 and interpolating between (h - d„)/Rg = 0.45 

 and (h - dg)/Rg = 0.50 to find the value of 0.^/% associated with 

 (h - dg)/Rg = 0.471 yield a value of Qr/Qm = 0.393; therefore, 



Q^ = 0.393 X 2.963 = 1.16 cubic feet per second per foot . 



Using Table 2 in a similar way to obtain a peak overtopping rate gives 



Qq g = 1.784 X 2,963 = 5.29 cubic feet per second per foot . 



Thus, Tables 1 and 2 give factors which can be multiplied by the mono- 

 chromatic overtopping rate, given by equation (1), to predict the average 

 and peak overtopping rates for irregular wave conditions. In addition. 

 Tables 1 and 2, along with Figure 2, give perspective on the degree of 

 conservatism or nonconservatism in the traditional monochromatic approach 

 to wave overtopping. 



Example problem 2 illustrates the output format of the computer 

 program given in the. Appendix. 



V. SUMMARY 



A proposed technique for predicting overtopping rates for irregular 

 wave conditions is presented. This technique is easy to use because it 

 can be applied as a "correction" to the method for monochromatic waves 

 shown in the SPM (U,S, Army, Corps of Engineers, Coastal Engineering 

 Research Center, 1975^; Weggel, 1976^), The technique has the further 

 value of providing insight on the degree of conservatism or nonconserva- 

 tism in the SPM monochromatic wave overtopping equation (eq. 7-6, eq, 1 

 in this report) for different wave and structure conditions. Insight of 

 this type can be used in evaluating the trade offs among structure height, 

 structure characteristics, and cost when determining the optimum struc- 

 ture design. 



Based on the analysis developed in this report, equation (Ij generally 

 predicts overtopping rates substantially greater than would be expected 



lU,S, ARMY, CORPS OF ENGINEERS, COASTAL ENGINEERING RESEARCH CENTER, 

 op, cit. , p, 7, 



^WEGGEL, op, cit,, p. 7. 



14 



