This slope may now be used with the runup curves (Figures 7-10 and 7-11) 

 to determine a second approximation to the actual runup. Calculate 

 dg/H^ using the breaker depth d^, , 



^ = ^ = 1.39 , 



Interpolating between Figures 7-10 and 7-11, for 



= 0.0024, 





= 1.55 . 



Correcting for scale effects using Figure 7-13, 

 k = 1.07 , 



and 



R = 1.55(1.07)5 * 8.3 ft. 



A new hypothetical slope as shown in Figure 7-22 can now be calculated 

 using the second runup approximation to determine Ax and Ay. A 

 third approximation for the runup can then be obtained. This procedure 

 is continued until the difference between two successive approximations 

 is nearly zero. The sequence of runup approximations for the example 

 problem is 



and the steps in the calculations are shown graphically in Figure 7-22. 

 The number of computational steps could have been decreased if a better 

 first guess of the hypothetical slope had been made. 



7.22 WAVE OVERTOPPING 



It may be too costly to design structures to preclude overtopping by 

 the largest waves of a wave spectrum. If the structure is a levee or dike, 

 the required capacity of pumping facilities to dewater a shoreward area 

 will depend on the rate of wave overtopping and water contributed by local 

 rains and stream inflow. Incident wave height and period are important 



7-37 



