developed by Bretschneider (1952, 1958, 1970) and incorporates the 

 results of Ijima and Tang (1966). The SPM method assumes that bottom 

 friction f^ = 0.01. The significant wave height and wave period are 

 obtained from empirical equations given as 



^ = 0.283 tanh 



0.530' 



0. 75 



tanh 



0.01251^ 



0.42 



tanh 0.530Pj 



WT7T 



CD 



and 



l-rr = 1.20 tanh 

 2TrU 



0.833 



gd 



0. 375 



tanh 



0.077 i^r" 



tanh 



P^'^(^^°'''' 



C2) 



where 



H = significant wave height 



T = significant wave period 



d = water depth 



U = windspeed 



F = fetch length 



g = gravitational acceleration. 



Since the terms are evaluated in dimensionless form, any consistent sys- 

 tem of measurements may be used. Equations (1) and (2) are plotted as 

 curves in Figures 1 and 2, respectively, for constant values of water 

 depth. Design curves for predicting the growth of waves in shallow water 

 for specified constant water depths are shown in Figures 3 to 12 (after 

 SPM, U.S. Array, Corps of Engineers, Coastal Engineering Research Center, 

 1975). 



III. CALCULATION OF ADJUSTED FETCH 



The long dashline in Figure 1 indicates the maximum significant wave 

 hei^t, H , which will occur for any given water depth and windspeed 



