This quasi-linear computational scheme can he used for manual com- 

 putations; however, since the calculations are repetitive, they can be 

 performed more efficiently by us,ing a digital computer. When carried out 

 manually, the technique is laborious, tedious and subject to error. 

 Bodine (1971) gives a computer program based on the numerical scheme 

 presented here. Other programs bas«d on similar niomerical schemes using 

 the quasi-static methods have been developed. 



When manual computation of storm surge is necessary, a systematic, 

 tabular procedure must be adopted to permit stepping through all of the 

 discrete computational points in space for each time increment. Table 

 3-10 represents a recommended procedure. One table is required for each 

 time increment. Table 3-10 corresponds to the time of peak surge for 

 Hurricane Camille; preceding tables required to bring the calculations to 

 this point are not included since those calculations are similar. The 

 first table in the series must reflect the initial conditions; thus V is 

 taken to be zero and S is assumed uniform over the system. 



Manual surge calculations for Hurricane Camille give a peak surge of 

 25.03 feet, say 25 feet (MLW) or 24.2 feet (MSL) . The bottom friction 

 coefficient selected for this particular example was K = 0.003 and the 

 surge was found to be insensitive to small changes in the friction coeffi- 

 cient. Computer calculations using a friction coefficient of 0.003 result- 

 ed in a peak surge of 25.19 feet and a bottom friction coefficient of 

 0.0025 resulted in a peak surge of 25.40 feet. For some basins and storm 

 systems, the bottom shear stresses are more significant in determining 

 water levels. Therefore, it is important to select a bottom friction 

 coefficient by verification (i.e., by comparing calculated results with 

 observed water levels). After such verification, the model may be used 

 to estimate the storm surge from hypothetical hurricanes for the same 

 geographical region. 



The surge hydrograph (water level as a function of time) for Hurricane 

 Camille is shown in Figure 3-50 for the most landward computational point 

 on the traverse line. This figure shows that the water level rose for 

 about the first 8 hours, hut then began to fall gradually until about 27 

 hours of computational period had elapsed, then began to rise rapidly. 

 A study of the local wind fields during this period shows that the winds 

 had an onshore component in the early stages of the storm, then the winds 

 began blowing offshore for several hours before the principal rise at the 

 coast. 



(b) Nomograph Method . A simplified method for obtaining 

 a first approximation to the peak storm surge of a hurricane can be based 

 on an empirical analysis of past records, an empirical analysis of a sys- 

 tematic set of calculations with numerical models, or a combination of the 

 two. Jelesnianski (1972) combined empirical data from Harris (1959) with 

 his theoretical calculations to produce a set of nomograms that permit the 

 rapid estimation of peak surge for any geographical location when a few 

 parameters characterizing a storm are known. 



The first nomogram (Fig. 3-51) permits an estimate of the peak surge 

 Sj, generated by an idealized hurricane with specified CPI and radius of 



3-115 



