where 



k' = a numerical constant as 0.003 



p^ = air density 



W = Wind velocity 



F = Fetch length 



G = angle between wind and the fetch 



n = 1 + '^s/'^b; 1.15 < n < 1.30 



AS = Wind setup. This value represents 

 the difference in water level 

 between the two ends of the fetch 



D = average depth of the fetch . 



An approximate expression of Equation 3-82 is given by 



CW^F 



AS = cos 6 (3-83) 



D 



where C is a coefficient having dimensions of time squared per unit 

 length. Saville (1952) in a comprehensive investigation of setup data 

 obtained from Lake Okeechobee found that C is approximately 1.165 x 10"^ 

 when W is given miles per hour, F in miles and D and AS in feet. 

 This coefficient is almost identical with that of the Netherlands Zuider 

 Zee formula (1.25 x 10"^). 



Equation 3-83 is often useful in making the first approximation of 

 the setup in an enclosed basin. Its advantage is that the setup can be 

 evaluated with fewer computations. The surge can be estimated more satis- 

 factorily by segmenting an enclosed basin into reaches and using a numeri- 

 cal integration procedure to solve Equation 3-81 for the various reaches 

 in the basin. Bretschneider (Ippen, 1966) presented solutions in parameter 

 form for Equation 3-81, and compiled these solutions in tables for different 

 conditions. These tables can be used to estimate the storm surge for a 

 rectangular channel of constant depth with either an exposed bottom or a 

 nonexposed bottom and a basin of regular shape. Such solutions may provide 

 an estimate of the water level variation in some basins. 



A more complete scheme than those described above follows. This 

 method accounts for the time dependence of the problem; more specifically 

 Equations 3-79 and 3-80 are used. Although this more complete method 

 provides a better approximation of the surge problem, it is done at the 

 expense of increasing the computations. 



3-130 



