13. The surf zone data collection group consisted of approximately 



15 members, and work was divided into four functional areas: sand trapping, 

 measuring currents, measuring waves, and beach profile surveying. These 

 labor-intensive experiments were performed under a range of wind sea and swell 

 conditions with moderate wave heights. Figure 3 shows the energy-based 

 significant wave height H^,* and spectral peak period T p for 11 to 

 23 September measured at FRF pressure gage 191. Gage 191 is located at FRF 

 longshore coordinate 990.4 m and cross -shore coordinate 914.4 m, at a depth of 

 -7.77 m relative to National Geodetic Vertical Datum (NGVD) , which at the FRF 

 is related to the mean sea level (MSL) datum by MSL(m) = NGVD(m) + 0.067. 

 Tide elevation as recorded on a gage located at the end of the pier is also 

 shown in Figure 3. During the 13 days of intensive data collection (11 to 

 23 September), H,„ ranged from approximately 0.03 to 1.6 m, and T p ranged 

 from approximately 3 to 14 sec. During most of the project, waves were 

 observed to arrive from slightly out of the southern quadrant, producing a 

 longshore current moving to the north with a magnitude in the range of 0.1 to 

 0.7 m/sec. Table 1 summarizes the wind and offshore wave regime during the 

 sand-trapping data collection period. 



14. A small rip current is frequently located just north of the FRF 

 property line. The data collection arrangement was designed to use the 

 southern longshore feeder current of the rip as a dependable source of a 

 steady and unidirectional longshore current when the direction of the current 

 generated by oblique wave incidence became confused. The longshore sand 

 transport rates and the current moving the sand were produced by combined 

 oblique wave incidence and the rip feeder current. In comparisons made to 

 theoretical expressions, it would be invalid to use predictive formulas for 

 either the longshore current or the longshore sand transport rate that are 

 solely functions of parameters related to obliquely incident waves. 



* For convenience, symbols and abbreviations are listed in the Notation (Appendix 

 B). 



11 



