Surf Porometer, f= (VL J° Cote 



Figure 8. Rdgs/Hg versus the surf parameter. 



and lower limits of data scatter about the trend-line curve. The trend- line 

 curve for relative rundown is given by the equation 



Rri 



98 



-2.46/5 



= -2.32e 



(6) 



The absolute value of relative rundown is small for small values of the surf 

 parameter since the plunging waves which dominate these conditions cause con- 

 siderable wave setup. As the surf parameter increases a standing wave develops 

 against the structure and the relative rundown approaches -1.75, although values 

 occasionally as low as -2.25 were observed. Equation (6) provides a simple way 

 to estimate the approximate lower limit of rundown. 



There is no scale-effect correction factor specifically developed for wave 

 rundown, so it is recommended that the correction factor for wave runup be 

 applied to rundown as illustrated in example problem 2 in Section V. 



IV. 



APPLICATION OF RESULTS TO ROUGH AND POROUS SLOPES 



The results given in this report can be applied to plane, rough- and 

 porous-slope structures, if there is. relatively deep water at the toe of the 

 structure (as discussed previously in Sec. II). To apply these results it is 

 necessary to have a reliable estimate of the rough-slope runup correction fac- 

 tor, r, which is the ratio of wave runup on a rough or porous slope to the 



14 



