The values of the dimensional constants Cj, C2, and C3 in Equations 

 3-74, 3-75 and 3-76 depend on the units used in performing the calculations. 

 Table 3-9 gives the dimensions of the variables used in the numerical 

 scheme in three systems of units and the corresponding value of the 

 constants for each system. The first column of units is given in the 

 metric system while the other two are given in mixed units in the English 

 system. 



Table 3-9. Systems of Units for Storm Surge Computations 



The assumptions for this model are reasonably good only when the 

 momentum of the water is increasing under the influence of the wind, i.e, 

 when the right side of Equation 3-76 is positive. This condition can be 

 considered in the calculations by using the relation 



^n + 1 ^ 



+ B, 



\n+l 



i+1 



(^%i 



2C, K 



(3-77) 



For a derivation of this equation see Bodine (1971). Should V at a 

 particular time level, as evaluated from Equation 3-76, be less than the 

 value obtained from Equation 3-77, then the result from Equation 3-77 is 

 ignored. However, if the opposite is true, then as an estimate, V is 

 taken equal to the maximiom possible value as given by Equation 3-77. 



3-108 



