at low tide. This measurement was for S^ taken_as a dependent variable. 

 Values ranged from 1.^ to ^.55 degrees. When S-^- was taken as an independ- 

 ent variable^ the slope was measiired over the distances shown on figure k. 



Ss 



Mean Slope of Beach Over Inner 



Portion of Shoaling-wave Zone 



The mean slope was determined for a 100-foot length of beach in the 

 shoaling-wave zone (fig. 3) where MLW depths ranged between 10.1 and lU.l 

 feet. Measurements of the altitude of five stations were made daily at 

 low tide in the summer, and every four hours in the winter. Mean slope 

 values used in the analyses ranged between O.5O and 2.22 degrees. 



Wave Period 



Wave period was determined from wave -spectrum- analyzer records fur- 

 nished by the Coastal Engineering Research Center. The period used was 

 the one corresponding to the peak value on the linear- average curve of 

 wave heights for the dominant wave train. (Period values thus obtained 

 were nearly always larger than those obtained in a "significant -wave" 

 chart analysis.) Values used ranged from 3-10 to 13. 90 seconds. 



Ua^ U^f^ U^n^ Up^ "s 

 Mean Wind Velocity Against the Direction of Longshore Current, U ; 



In An Offshore Direction, UQf ; In An Onshore Direction, U^^^; 



Parallel to Shore U ; And in the Same Direction as 



the Longshore Current, Ug. 



Mean wind velocities and directions were recorded at 2-hour intervals 

 at the Cape Henry weather station (fig. li), some 7-5 miles north of the 

 study area. The deviations in wind directions permitted when describing 

 the direction as onshore, offshore, and so on, are given below: 



^a ^— ^^° °-^ wind vector directed opposite to longshore- 

 current flow) 



^of ^— ^'^ ^■^ wind vector perpendicular to shore and in 

 an offshore direction) 



U (+80 of wind vector perpendicular to shore and in 



on 



an onshore direction) 



61 



