From Figure 18 for d/H^ = 5 and H^/gT 2 = 0.0038, 

 — % 1.2 



R = jlrj (H^) = (1.2) (3.05) = 3.66 meters (12.0 feet). 



(See Sec. VI for the appropriate scale-effect correction factor.) 



************************************ 



************* EXAMPLE PROBLEM 7************** 



GIVEN: A structure is designed geometrically similar to that in example 

 problem 5, where an impermeable, smooth, 1 on 2 structure is fronted 

 by a 1 on 10 beach slope. Toe depth for the structure is d s = 3.0 

 meters but the beach slope extends seaward to a depth of 15.0 meters 

 beyond which the slope is approximately 1 on 100. However, a range 

 of wave periods and deepwater wave heights are known; 



W } < 5.0 meters (16.4 feet) . 



FIND : ' Determine maximum runup for three different wave conditions: 

 T max = 7 -° seconds; l max = 13.0 seconds; and constant wave steep- 

 ness, H^/gT 2 = 0.0104, with T max = 7.0 seconds. 



SOLUTION : For any given dg/H^ value, the design curves show that 

 relative runup is highest for the longest wave period (or the 

 lowest wave steepness, H^/gT 2 ) . However, for constant toe depth, 

 dg, and for constant wave steepness, the largest wave height (or 

 lowest dg/H^ value) usually results in the largest absolute runup, 

 R. When a sloping beach is present and wave steepness varies, with 

 depth held constant, the maximum runup may occur at a dg/H^ value 

 other than the minimum. Thus, runup for a range of dg/H^ values 

 should be investigated for this example problem. 



(a) For the first condition where Imax - 7.0 seconds, the 

 maximum wave height given is H^ = 5.0 meters; for this location, the 

 resultant dg/H<J, value is 



H ^ - j - 0.6 , 



which corresponds to the lowest value given in Figures 20 to 23. 

 The maximum runup may be determined by constructing a table for 

 varying conditions. Because the maximum wave period is less here 

 than in example problem 5, L is also less; thus, £/L > 0.5 and 

 Figures 20 to 23 may be used. For ds = 3.0 meters, T = 7.0 seconds, 

 and gT 2 = 480.20 meters (1,576.0 feet), Table 3 may be constructed 



57 



