Table 5 

 Comparison Between Measured and Hindcast Waves 

























Measured 



Hindcast 



Comparison 



Hindcast 



Comparison 





Wave 



s 



Sep 



- Nov 



Sep 



- Nov 



Apr 



- Nov 



Apr - Nov 



Month 



H 

 ft 



1.2 



sec 



4.7 



H h 

 ft 



1.5 



sec 



2.4 



H/H h 

 0.8 



T p /T h 

 1.9 



H h 

 ft 



T h 

 sec 



H/H h T p /T h 



Sep 



-- 



.. 



Oct 



2.0 



4.9 



1.4 



2.3 



1.4 



2.1 



-- 



-- 



-- 



Nov 



1.6 



4.7 



1.7 



2.5 



0.9 



1.9 



-- 



-- 



-- 



AVG 



1.6 



4.7 



1.5 



2.4 



1.0 



2.0 



1.5 



2.4 



1.0 1.9 



Note: H = measured significant wave height; Tp = measured peak wave period; 

 H h = hindcast significant wave height; T h = hindcast significant wave period. 



383. As seen from Table 5, there was good agreement between wave 

 heights for the two data sets, whereas the period for the measured waves is 

 about twice that of the hindcast. Assuming that the measurements are repre- 

 sentative, the hindcast was modified by multiplying the periods by a factor of 

 2, with the constraint that the wave period could not be greater than 8 sec. 

 The result of this transformation to a new wave data file called WAVES_2T is 

 illustrated by sample lines in Table 4. 



384. The GDM (USAED, Buffalo 1975; Walker, Clark, and Pope 1980; Pope 

 and Rowen 1983) derived estimates of the longshore sand transport rates 

 described above using an equation similar to Equation 2 with Kl = 0.77 and 

 K2 = 0.0 . Therefore, to be compatible with the original estimates made by 

 specialists who knew the coast, the same values were used to calculate annual 

 potential transport rates for a straight shoreline without structures. The 

 calculated rates should correspond to the previously reported potential rates. 

 Table 6 shows selected calculated transport rates obtained using the modified 

 WAVES file. 



385. As shown in Table 6, with a positive transport rate defined from 

 west to east, the calculated annual net transport rate was of the correct 



163 



