It can be seen in Figure 12 that the new conservative runup curve provides a 

 envelope for the observed data. The conservative curve would be expected to 

 exceed about 97.7 percent of the data. An exceedance level of 97.7 percent is 

 obtained from a standard normal distribution table for a value two standard 

 deviations greater than the mean. Figure 12 helps confirm the method of 

 choosing an envelope curve by showing only one observed value above the con- 

 servative curve. This is approximately what would be expected for a normal 

 distribution with a sample size of 69. Other curves used to predict maximum 

 runup could be constructed which would be more or less conservative than the 

 example just provided. The degree of conservatism would be evaluated on the 

 basis of the risk posed by waves overtopping the revetment. 



20. Since the standard surf parameter has been frequently used to pre- 

 dict wave runup, it is useful to provide a prediction formula based on that 

 method to allow comparison to earlier studies. Using Equation 3 to define the 

 surf parameter in Equation 5, the runup coefficients were determined for the 

 combined NCE and SAJ data sets as a = 1.022 and b = 0.247 . Figure 13 

 shows the predicted and observed values of Rjnax/Hjno versus the standard surf 

 parameter. It can be seen that the predicted values follow the trend of the 

 observed data very well. Using the same method to evaluate errors as was used 



3.5 



PLUNGING REGION 



(LARGE WAVES 

 PLUNGE DIRECTLY 

 - ON RIPRAP) 



TRANSITION 

 REGION 



i 



i i 



SURGING REGION 



(SURGING OR STANDING WAVES 



AGAINST STRUCTURE! 













■ ■ 





3.0 







■ 



■ ■ * ^^ 



- 



2.5 





. ^ 



■ ^ 





" 



2.0 





m m 3i 





m 



" 



15 



■ 

 ■d 





■ 





- 



1.0 



*r* 







LEGEND 



- 



OS 



j 





i 



■ OBSERVED DATA 

 mm PREDICTED STANDARD SURF 



1 1 



" 



Figure 13. Comparison of the prediction of R^x using 5 



21 



