conservative; i.e., the predicted wave heights are expected to be slightly 

 higher than the wave heights which actually occur. 



Wave prediction curves for waves passing through shallow water where 

 the bottom friction, fj? = Q.01, are shown in Figures 1 and 2. For any 

 given windspeed, U, and water depth, d, there is a maximum (depth- 

 limited) significant wave height, H gm , which would be generated (long 

 dashline in Fig. 1). 



Where Fb, the initial wave height at the seaward or beginning edge 

 of the fetch, is less than H sm , the wave would increase in height. 

 Where the bottom friction, ff > 0.01, the wave would not become as high 

 as a wave traveling over a bottom where ff- 0.01, with the segment fetch 

 distance, Ax, being the same in both cases. Therefore, an adjusted 

 fetch, F Q < Ax, would be used to describe the wave, using Figures 1 and 

 2 which were developed for the case of ff = 0.01. Except for specific 

 water depths, Figures 3 to 12 (after SPM) show the same results as Figures 

 1 and 2 . 



Where H^ > H gm , the wave would decay. As a value of ff > 0.01 would 

 cause a wave to decay a greater amount than if it were traveling over a 

 bottom where ff = 0.01, an adjusted fetch, F a > Ax, would be used in 

 this case. 



The details of this method are discussed by Camfield (1977) 2 . 



II. FETCH ADJUSTMENT 



The fetch should initially be divided into segments so that (a) 



Ad < 0.25 &i (1) 



where Ad is the change in depth over the distance across the segment in 

 the direction of wave motion, and d^ is the depth at the seaward or 

 beginning edge of the segment; (b) 



Af f < 0.25 f fi (2) 



where hff is the change in the bottom- friction factor over the segment 

 distance, and ffi is the bottom-friction factor at the beginning edge 

 of the segment; and (c) after computation of the wave height at the end 

 of the fetch, 



AH < 0.5 Hi (3) 



where AH is the change in the wave height over the segment distance and 

 Hi is the wave height at the beginning edge of the segment. Each segment 

 of the fetch can then be considered separately using the method indicated. 



2 CAMFIELD, F.E., "Wind-Wave Propagation over Flooded, Vegetated Land," 

 TP 77-12, U.S. Army, Corps of Engineers, Coastal Engineering Research 

 Center, Fort Belvoir, Va. , Oct. 1977. 



