18. The bottom profile along the photopole line was surveyed each day 

 by means of an infrared beam total survey station housed at the main building 

 of the FRF (cf Table A5 of Appendix A for the profile survey data). These 

 surveys were supplemented by standard transit surveys performed from the base 

 camp and by wide -area surveys taken by the CERC Coastal Research Amphibious 

 Buggy (CRAB). Howd and Birkemeier (1987) and Ebersole and Hughes (1987) 

 present wide -area bathjnnetry data. The near shore bathymetry in the vicinity 

 of the base camp remained predominantly two-dimensional during the trap 

 experiments. The foreshore had a steep slope covered by pebbles for approxi- 

 mately 5 m, and relatively high waves (20-50 cm) frequently broke directly 

 upon it. Since there was no sand surface on the step and the pebbles did not 

 appear to move alongshore, traps were not placed on the step. Seaward of the 

 step, the profile fell steeply then rose to either a bar or a plateau that 

 extended across much of the surf zone. The surf zone bottom seaward of the 

 step consisted of a fine-grained sand substrate with a median grain size of 

 0.17 mm. 



19. The mean water level was obtained at 6-min intervals from a tide 

 gage located at the seaward end of the FRF pier (Table A4, Appendix A). Water 

 levels are referenced to the National Geodetic Vertical Datum (NGVD) , which is 

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

 maximum tidal variation observed during the experiment was approximately 1 m 

 (Figure 3). Local mean water levels across the surf zone are tabulated in 

 Ebersole and Hughes (1987) for individual experiment runs. 



Surf zone currents 



20. Water flow was measured with two 2-component Model 551 Marsh- 

 McBirney electromagnetic current meters. The meters were mounted on newly 

 designed tripods and connected to shore by cable to recorders located in the 

 instrument trailer. The tripods, shown in Figure 5, are made of 1.9-cm 

 (3/4-in.) stainless steel and stand approximately 1.5 m high. The lower ends 

 of the tripod legs were sunk into the bed to a depth of about 10 cm by shaking 

 the tripod back and forth and applying downward pressure. A tripod with 

 current meter attached was easily moved by two individuals, permitting its 

 rapid relocation in the surf zone in response to varying tide level, wave 



16 



