USING THE CRITICAL PROFILE OVERLAY 



When the critical profile has been plotted, it is superposed on the 

 study area profiles by matching the intersection of the design SWL and the 

 vertical axis on the overlay with the intersection of the design SWL and 

 the structure slope on the study area profile (see Figure 3). If, as in 

 Figure 3, the critical profile for HJ/T 2 = 0.20 always lies below the study 

 area profile, the structure should be safe from overtopping for all waves 

 with Hq/T 2 = 0.20. Also, the structure should be safe from overtopping for 

 all waves of H^/T 2 = 0.10 even though the critical profile for that wave 

 steepness lies above the study area profile between points (a) and (b) shown 

 on Figure 3. This conclusion is reached because waves which would ordinar- 

 ily break in the critical area between (a) and (b) will break farther out 

 on the bar crest at (c) and smaller waves will not break until they have 

 passed shoreward of (b) where the study area profile is safe. 



2 

 In Figure 5, the study area profile is safe for all waves of H*/T = 



0.20 but unsafe for some waves of HVT 2 = 0.10. The waves which would over- 

 top the structure in this case would be those that would break between (a) 

 and (b), Figure 5. If the study area profile followed the dotted line shown, 

 the structure would be overtopped by some wave heights of both wave steep- 

 nesses shown and the structure would be moved farther shoreward or its height 

 increased in the area of this profile. 



In cases where sandy beaches are being considered, it might be wise to 

 consider the possibility of some profile recession during a storm. Some 

 idea of the magnitude of the recession can be obtained from Reference 6. 



CONCLUSION 



A method has been presented for checking more rapidly the design height 

 of shore structures along a beach fronted by differing offshore profiles. 

 The accuracy of the method is limited by the accuracy of the existing wave 

 run-up relationships and the accuracy of the solitary wave theory as applied 

 to surf conditions. However, when the method is judiciously applied, it 

 offers a quick comprehensive check of the adequacy of structure height to 

 prevent wave overtopping. 



