The initial setup refers to the water level at the time the storm surge 

 computations are started. An approximate relationship giving the atmos- 

 pheric pressure setup in feet when pressure is expressed in inches of 

 mercury is 



Sap = 1-14 (p„-pj d-e-'^) 



(3-71) 



where p„ is the pressure at the periphery of the storm, and r is the 



radial distance from the storm center to the computation point on the 

 traverse line. 



The total depth at the new time level is evaluated by the relation: 



D 



n + 1 



+ 'A 



d,.+ d,.^, 



+ s, + s^"^+ (s. + sj;,, 



'A 



(3-72) 



(Sap), + (s^p),.,] 



n + l 



The total water level rise at the coast is the sum of all component water 

 level changes resulting from the meteorological storm plus those components 

 which are not related to the storm. Hence the total setup is given by 



s. + S3, + s^p + s, + S^ + S^ + S^ 



(3-73) 



where Sj/ is a component due to the wave setup in the region shoreward of 

 the breaker line and is related to the breaker height by Equation 3-49. 

 (See Section 3.85, Wave Setup.) The setup component S^ accounts for the 

 setup resulting from local conditions such as bottom configuration, coast- 

 line shape, or other flows influencing the system, such as flows from bay 

 inlets or rivers. This component can only be estimated from a full under- 

 standing of the influence of topographic and hydrographic features not 

 considered in the numerical calculations. Contributions made by the 

 various setup components to the total surge are shown in Figure 3-46. 



Equations 3-65, 3-66, and 3-67 can be rewritten in a more useful form 

 by introducing dimensional constants for terms frequently appearing in the 

 equations. Hence, 



(As.)r;4 



C, Ax 



1 Ax 

 A. 



+ ^.l) 



n+l 



(3-74) 



i+'A 



(-^)::i 



C2 Ax 



D' 



n + l 

 i+'A 



(sm0),. + (sin0).^^] V^^,)^ 



(3-75) 



n + l 

 ^i+'A 



(B, + B.,,)«+(B, + B.,,)«-^](At)+ V",, 



l+C3lV«,^JAtK(D-)r;^^ 

 3-106 



(3-76) 



