where: 



Q = sediment volume transport 



K = empirical coefficient 



P,j = longshore energy flux 



Pj = density of sand 



a' = volume concentration (0.6) 



Also see Galvin (1979) and Galvin and Schweppe (1980). 



Since the wave measurements were in deep water or nearly so, small-amplitude 

 wave theory approximations were used to obtain the breaker line P,s value from 

 deepwater values using SPM (1984) Equation 4-45: 



/>j^ =0.05p^"'i//''(cosa(,)'"'sin2a„ (3) 



where Hq is the deepwater significant wave height and Oq is the deepwater wave 

 angle. A deepwater depth (dg) was calculated from the peak period (T^) as: 



d^ = 0.78 r, - (4) 



If this depth was greater than die gage deptii, the wave height and angle were 

 back-shoaled to obtain deepwater values for Equation 3. 



Then the transport rate for each wave record was calculated from 

 Equation 2 as: 



Q = o.np,^ (5a) 



in cubic meters per hour for the DWG records or as: 



Q = 0.40 P,^ (5b) 



in cubic meters per 3-hour period for the Puv wave records. Equations 5a and 

 5b use a value of K = 0.35, since the significant wave height is being used. No 

 attempt was made to alter this coefficient to adjust the results. 



These values were then summed to produce transport rates per month. 

 Since the wave data record had some gaps and also multiple years of data for 

 some months, this monthly rate was multiplied by the number of possible data 

 points in a month and divided by the number of actual data points that month. 

 This produced the comparable monthly values shown in Figure 26. These rates 

 were then summed to produce the yearly averages shown in Table 12 for the 

 vicinity of Colorado River, TX. This method meant that months with fewer 

 data points were more heavily weighted than months with more data. It was 

 felt that this gave a more representative value of longshore transport than an 

 equal weighting scheme, given the seasonal variation in wave climate shown in 

 Figures 11 and 12. The values are fairly similar to that of Heihnan (1995) (see 

 Table 11, line 8) because the same data set and a similar procedure were used. 



Chapter 5 Prediction of Sediment Transport Rates 



45 



