Table 4. Shoreline orientation as determined from 

 beach and offshore profiles. 



Date of survey 



Range of effective shoreline 

 orientation relative to base line 



8 May 1974 

 18 June 1974 



9.95° to 11.33° 

 8.83° to 10.78° 



Value adopted 

 in this study 



10.07° 



4. Results of Longshore Sand Transport-Longshore Energy Flux Factor Correlation. 



In the correlation of Pj^g with I, only the values directed toward the trap 

 were used. The rationale is that during all periods when waves were directed 

 toward the trap, there was sediment available for transport; therefore, this 

 variable provides the best basis for correlation. 



The volumetric accumulations were interpreted as I values by equation (3) , 

 using p = 0.35, and by dividing the time (in seconds) between surveys. 



In phase I of the study (April 1974 to September 1975) , the available values 

 of longshore energy flux factor were computed using wave gage data. Longshore 

 energy flux factors were also computed using LEO data during the same period 

 but, as discussed previously, for higher waves the LEO wave heights, in com- 

 parison with wave gage data, were typically underestimated so the LEO data were 

 not used in phase I. The wave gage data were available nominally every 2 hours. 

 The value of P^g for a survey period was obtained by summing all P^g values 

 directed toward the trap and dividing by the total number of wave recordings. 



In phase II (January 1976 to August 1977) , only data from one wave gage 

 were available for a limited time; therefore,, it was not possible to analyze 

 directional wave spectra to compute the longshore energy flux factor. As dis- 

 cussed earlier, the LEO wave height observations during phase II did correlate 

 reasonably well with wave gage data. As a result, the longshore energy flux 

 factor was computed using LEO data and the LEO current method presented in 

 equation (9) . 



Table 5 provides a summary of the analyzed data in phases I and II. Figure 

 17 presents the same data along with the SPM volumetric sand transport relation- 

 ship converted to the more common relationship of equation (1) between the 

 longshore energy flux factor and the immersed weight sand transport rate (in 

 metric units). In this relationship, the constant K is dimensionless and 

 ranges from 0.42 to 1.51 in the phase I data and from 0,19 to 4.18 in the phase 

 II data. The average value for the two sets of data is K = 0.98 with a break- 

 down for the two sets as follows: 



Phase No. of date 



I 

 II 



7 

 11 



K 



0.87 

 1.05 



K 



0.33 

 1.08 



'K/K X 100 

 (pet) 



38 



103 



36 



