For the remaining part of this problem, either the value of F^„ equal 

 to 220 nautical miles as determined from Figure 3-15 for U^ = 91.6, 

 Hq = 59.4 can be used with the deepwater forecasting curves, or else 

 Equation 3-40 can be used, as modified, 



H^ = 0.0555 U^ >JfJ + AF" 



along with Equation 3-36 



To = 2.13 V?^ . 



Fg is defined below. 



The latter being a numerical method is easier to use and more accurate 

 than the graphical method of using forecasting curves . 



The procedure for computing wind waves over the Continental Shelf 

 will be illustrated by using the bottom profile off the mouth of the 

 Chesapeake Bay and the standard project hurricane developed for the 

 Norfolk area. The storm surge computed for the standard project hurricane 

 and 2.5 feet of astronomical tide are added to the mean low water depths 

 to obtain the total water depth for wave generation. Refraction is 

 neglected in this example, i.e., K^ = 1.0. The results of these computa- 

 tions are given in Table 3-4 followed by examples and explanations. 



Column 1 of Table 3-4 is the distance in nautical miles measured 

 seaward of the entrance to Chesapeake Bay, using increments of 5 nautical 

 miles for each section. 



Column 2, d^, is the depth in feet referred to mean low water at the 

 shoreward end of each section, denoted by X of Column 1. 



Colvimn 3 is the depth dj at the beginning of each section. 



Column 4 is the depth 6.2 at the shoreward end of each section. 

 These depths are the water depths below MLW plus the 2.5-foot astro- 

 nomical tide plus the hurricane surge and are then rounded off to the 

 nearest foot. 



Column 5, d„, is the average of Columns 3 and 4 to the nearest foot. 



Column 6 is the effective fetch Fg (nautical miles), and is 

 obtained for the first step directly from Equation 3-40. For successive 

 steps, Fg = Fg + AF < 137 n.mi. where Fg is given in Column 14 one line 

 above in each case (e.g., line X = 40, Fg = 80.6 + 5.0 = 85.6) and AF is 

 5 n.mi. Fg is defined for Column 14. 



3-65 



