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 

 berm becomes flooded or the water depth increased by wave setup (see 

 Sections 3.8 and 3.85) such as a reef, the wave rionup is based on the 

 water depth on the berm or reef. 



************** EXAMPLE PROBLEM *************** 



GIVEN : A smooth-faced levee (cross section shown in Figure 7-21) is sub- 

 jected to a design wave having a period T = 8 sec. and an equivalent 

 deepwater height H^ = 5 ft. The depth at the structure toe is dg = 4 ft. 



FIND ; Using the composite-slope method, determine the maximum runup on 

 the levee face by the design wave. 



SOLUTION ; The runup on a 1 on 3 slope is first calculated to determine 

 whether the runup will exceed the berm elevation. Calculate, 



d. 



4 



ST = 5 = "■«• 



and 



H' 



gT^ 32.2 (8)^ 



= 0.0024 



From Figure 7-10 for 



H' 



0.8, 



with 



and 



cot(0) = = 3, 



5 



H' 



tan d 



0.0024 



= 2.8 



This runup is corrected for scale effects by using Figure 7-13 with 



tan 9 = 0.33 and H «= 5 ft. A correction factor of k = 1.15 is -obtained, 



^^ R = 2.8 kH; = 2.8 (1.15) (5), 



R = 16.1 ft . 



which is 10.1 feet above the berm elevation. (See Figure 7-21.) 

 Therefore, the composite-slope method must be used. 



7-34 



