(b) Riprap on a slope decreases the maximiira runup. Hydraulic model 

 studies for the range of possible slopes have not been conducted; 

 however. Figure 7-15 can be used with Figures 7-10 and 7-11 to 

 estimate the percent reduction of runup resulting from adding 

 riprap to a 1 on 1.5 slope and to apply that reduction to struc- 

 tures with different slopes. From an analysis similar to the 

 above, the runup, unoorreoted for scale effects, on a 1 on 1.5 

 smooth, impermeable slope is. 



= 3.1. 



smooth 



From Figure 7-15 (riprap), entering with H^/gT^ = 0.0033 and 

 using the curve for dg/H^ =1.5 which is closest to the actual 

 value of 



Hi 



1.48 



= 1.5 



rtprap 



The reduction in runup is therefore 



PV^] riprap 

 [^/^o] smooth 



1.5 

 3.1 



0.48 . 



Applying this correction to the runup calculated for the 1 on 2.5 

 slope in the preceding part of the problem. 



R. 



rip rap 



0.48 R 



looth 



= 0.48(21.3) = 10.3 ft 



Since the scale-corrected runup (21.3 ft.) was multiplied by the 

 factor 0.48, the correction for scale effects is included in the 

 10.3 ft. runup value. This technique gives a reasonable estimate 

 of runup on riprapped slopes when model test results for the 

 actual structure slope are not available. 



* * * * 



Saville (1958a) presented a method for determining runup on composite 

 slopes using experimental results obtained for constant slopes. The 

 method assumes that a composite slope can be replaced by a hypothetical, 

 imiform slope running from the bottom, at the point where the incident 

 wave breaks, up to the point of maximum runup on the structure. Since 

 the point of maximum runup is the answer sought, a method of successive 

 approximations is used. Calculation of runup on a composite slope is 

 illustrated by the following example problem for a smooth-faced levee. 



7-33 



