sea state may be represented by the effects of an equivalent monochromatic 

 wave of the same height and length. Losada and Gimenez-Curto (1980) have ap- 

 plied this principle and Equation 30 to several joint distribution functions 

 for H and T to derive distributions of runup that compare well with experi- 

 mental data. The SPM (1984) proposes a more expedient method which assumes the 

 runup heights will have a Rayleigh distribution. An alternative expedient 

 method has been proposed by Andrew and Smith (in preparation) which assumes a 

 Rayleigh distribution of wave heights and a constant wave period equal to the 

 period of peak energy density. The resulting distribution of runup heights is 

 not Rayleigh distributed, in keeping with the joint effect of height and pe- 

 riod as predicted by the runup formulae above. Interactive programs written 

 in BASIC for microcomputers are available from WES to estimate both runup and 

 wave transmission by overtopping by this technique.* An example of trans- 

 mitted wave height exceedance probabilities estimated by this method is pre- 

 sented in Figure 14. 



76. The principle of equivalence may not remain the key to prediction 



BREAKWATER 



) 30 40 50 60 



ESTIMATED % EXCEEDANCE 



70 

 [H>H,] 



Figure 14. Predicted transmitted wave 

 height exceedance probabilities 



US Army Engineer Waterways Experiment Station, Coastal Engineering Re- 

 search Center, in preparation, "Wave Runup on Rough Slopes: Computer Pro- 

 gram WAVHUNUP (MACE-14)," Coastal Engineering Technical Note, Vicksburg, Miss. 



, in preparation, "Wave Transmission by Overtopping: Computer 

 Program WAVTRMS (MACE-13)," Coastal Engineering Technical Note, Vicksburg, 

 Miss. 



51 



