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Method 1 



If the deepwater wave conditions, H^ and T, and bottom slope, m, 

 are known, use the following procedure for predicting nearshore signifi- 

 cant wave height: 



a. Determine the ratios, H^/gT 2 and d/gT 2 , where d is the 

 Stillwater depth at the point of interest. 



b. Enter the appropriate graph corresponding to the bottom slope, 

 m, with the value of d/gT 2 on the ordinate. Find the point where 

 d/gT 2 and H^/gT 2 intersect and read the value of (H s /d) off the 

 abscissa. 



c. Finally, H s = d(H s /d). 



Method 2 



If local conditions at one location are known ((H s ) i , d± , m, Tj the 

 significant wave height, (H s )2, at another shallower depth, dz, can 

 be determined: 



a. Compute (H s ) i/dj and d^/gT 2 , enter these values on the 

 abscissa, ordinate, and determine where they intersect. 



b. Determine the H^/gT 2 where the values intersect. Hq can be 

 found directly; (H s /d) 2 and (Hg) 2 can De found as illustrated 



in method 1 . 



III. EXAMPLES OF USE 



*************** EXAMPLE i**************** 



GIVEN : The conditions m = 0.02 (1 on 50 slope), T = 9 seconds, and 

 H^ = 8.2 feet (2.5 meters). 



FIND: The significant wave height where d = 6.56 feet (2.0 meters). 

 SOLUTION: Using method 1, 



and 



m/gT 2 = — ^ — o = 0.0031 

 ° /S 32.2(9) 2 



d/gT 2 = 6.56 = 0.0025 

 /B 32.2(9) 2 



From Figure 4, (H s /d) = 0.75; 



therefore, 



H s = d (H s /d) = 6.56(0.75) = 4.9 feet (1.5 meters) 



15 



