(i) Calculate the decayed wave height at the end of the 

 fetch by 



% = ^ " G i ("m - H sm) • (13) 



As a conservative estimate, it is assumed that the wave period 

 remains constant as the wave decays. 



V. SAMPLE DESIGN PROBLEMS 



The following examples demonstrate the use of the techniques discussed 

 in this report in the solution of design problems. Refer to the SPM 

 (U.S. Army, Corps of Engineers, Coastal Engineering Research Center, 

 1975) 1 for other information related to the total design problem (e.g., 

 wave theory, storm surges, wave setup, wave breaking, runup, etc.). 



***********.*** EXAMPLE PROBLEM l************** 



GIVEN : A wave passes into shallow water over a flooded coastal area. 

 The water depth, d£, at the seaward edge of the area is 23 feet 

 (7 meters), and at the landward edge of the area the depth is 13 feet 

 (4 meters) . The distance across the area in the direction of wave 

 motion is 10,000 feet (3,050 meters). The wave height, H^, at the 

 seaward edge of the area is limited by large sandbars seaward of the 

 area being considered and is 3 feet (0.91 meter), and the wave period 

 is 3.2 seconds. The windspeed is 70 miles per hour (31.3 meters per 

 second). The flooded area is covered with thick stands of tall grass. 



FIND : The height and period of the significant wave at the landward 

 edge of the segment. 



SOLUTION : 



0.25 d^ = 0.25 (23) =5.75 feet 



Ad = 23 - 13 = 10 feet > 0.25 d^ . 



Since this does not meet the condition of equation (1), the area should 

 be divided into two fetch segments. Assuming a uniform variation in 

 depth, take the first segment as a distance Ax = 5,000 feet with a depth 

 variation from 23 to 18 feet. Then 



Ad = 23 - 18 = 5 feet < 0.25 d£ . 



At the 23-foot depth (from Fig. 13, curve B) , 



ff = 0.080 



lU.S. ARMY, CORPS OF ENGINEERS, COASTAL ENGINEERING RESEARCH CENTER, 

 op. cit . , p. 9. 



28 



