**************** *EXAMPLE PROBLEM 4************** 



GIVEN : An impermeable structure has a smooth slope of 1 on 2.5 and is 

 subjected to a design wave, H = 2.0 m (6.6 ft) measured at a gage located 

 in a depth d = 4.5 m (14.8 ft) . Design period is T = 8 sec . Design 

 depth at structure toe at high water is d = 3.0 m (9.8 ft) . (Assume no 

 change in the refraction coefficient between the structure and the wave 

 gage.) 



FIND: 



(a) The height above the SWL to which the structure must be built to 

 prevent overtopping by the design wave. 



(b) The reduction in required structure height if uniform-sized riprap is 

 placed on the slope. 



SOLUTION: 



(a) Since the runup curves are for deepwater height H' , the shallow-water 

 wave height H = 2.0 m(6.6 ft) must be converted to an equivalent deepwater 

 value. Using the depth where the wave height is measured, calculate 



f..ULd, 2.(4.5) 0,3^ 

 o gT^ (9.8) (8)^ 



From Table C-1, Appendix C, for 



7^ = 0.0451 

 o 



o 



Therefore 



% = -dri=Mi= 1-9- (6.2 ft) 



To determine the runup, calculate 



-% = ^-^ X = 0.0030 



gT^ (9.8) (8)^ 



and using the depth at the structure toe 



d = 3.0 m (9.8 ft) 

 6 



7-33 



