^=K3S 





The reduction in runup is therefore. 





riprap ^ ^^ 



,, 3.04 "-^^ 

 smooth 



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

 the preceding part of the problem gives 



R . = 0.47 R ^, = 0.47 (5.8) = 2.7 m (8.9 ft) 

 riprap smooth 



Since the scale-corrected runup (5.8 m) was multiplied by the factor 0.47, 

 the correction for scale effects is included in the 1.7-m 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 with a hypothetical, uniform 

 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. The method is equally applicable to 

 any composite slope. The resultant runup for slopes composed of different 

 types of surface roughness may be calculated by using a proportionate part of 

 various surface roughnesses of the composite slope on the hypothetical 

 slope. The composite-slope method should not be used where beach berms are 

 wider than L/4 , where L is the design wavelength for the structure. In 

 the case where a wide benn becomes flooded or the water depth has been 

 increased by wave setup (see Ch. 3, Sec. VIII) such as a reef, the wave runup 

 is based on the water depth on the berm or reef. 



**************** EXAMPLE PROBLEM 5************** 



GIVEN : A smooth-faced levee (cross section shown in Fig. 7-21) is subjected 



to a design wave having a period T = 8 s and an equivalent deepwater 



height H' = 1.5 m (4.9 ft) . The depth at the structure toe is d = 1.2 m 



(3.9 ft) •? ^ 



FIND: Using the composite slope method, determine the maximum runup on the 

 levee face by the design wave. 



7-35 



