which are computed from significant wave height, Komaf's values for P^g 

 are multiplied by a factor of 2 before being used in the SPM (see App . B) . 



Two additional sources of field data are included in Figure 6 of Das (1972), 

 a plot of Q versus Pig similar to Figure 4-36 of the SPM. These sources 

 are 5 data points from Johnson (1952) and 14 data points from Thornton (1969) . 

 Neither source is included in Figures 4-36 and 4-37 of the SPM nor are they 

 used in the derivation of the empirical relation between Q and Pis> equation 

 (C-1) . Johnson's data do not include wave direction, but the corresponding 

 points must plot above the line given by equation (C-1) in Figure 4-37 for 

 reasons given in Galvin and Vitale (1977). Thornton's data are from bedload 

 traps between the inner and outer bar, and represent minimum values of Q. 



The design prediction (eq. C-1) is based solely on field data, but Figure 

 4-36 does show laboratory data for comparison. Das (1971) lists 177 laboratory 

 data points, and of these, 161 are shown in Figure 4-36 of the SPM. In the two 

 data points from Price and Tomlinson (1968) , crushed coal with a specific grav- 

 ity of 1.35 (as opposed to 2.65 for the quartz that makes up most beach sand) 

 was used. In 14 of the 17 data points from Sauvage and Vincent (1954), sedi- 

 ments with specific gravities of 1.1 and 1.4 were used. Thus, these 16 light- 

 weight data points were not included in Figure 4-36. 



The longshore energy flux, Pj^s , for the laboratory data was computed, 

 using equation (32) of Das (1972) 



1 P^ 9 9 

 Po^ = T-^^ L NK^ sin a, cos a, (C-12) 



Is 2 8 o o R b b ■' 



Wq is the deepwater wave height, Lq is the deepwater wavelength, and N is 

 the number of waves per day, given by 



N = (86,400 seconds per day) 



where the period, T, is measured in seconds, and K^^ is the refraction 

 coefficient. The leading factor of 1/2 in equation (C-12) is the deepwater 

 approximation for n as given in equation (C-3) . 



The value for Eq comes from 



H' 



{%) 



^^h 



(C-14) 



where . 



H/H' is obtained from Wiegel's tables (SPM, App. C, Table C-1), and the 



33 



