bar-trough rhythms. Because an artificial beach-nourishment project has 

 been in operation within the study area since 1956, the measurements for 

 this study were taken during times of little or no pumping of sand. 



Physical and dynamic properties of 219 sand samples from the area 

 have been studied by Harrison and Morales-Alamo (196U), and the averages 

 of several properties for various dynamic zones of the beach may be sum- 

 marized as follows: 



Zone 



Mean Size in mm 



Nominal 



Dia. 



Sieve 

 Dia.* 



Sorting Reynolds Number 

 Coefficient (Under Average Sea- 

 Water Conditions) 



Shoallng-wave 



0.25 



0.22 



0.70 



U.8 



Breaking-wave 



0.30 



0.27 



0.70 



8.1 



Swash 



0.28 



0.25 



0.55 



6.2 



Swash-berm 



0.37 



0.33 



0.5^ 



12.0 



^Converted from nominal diameter (Int.-Agcy Comm. Wat. Res., 1957, fig. 5) 



Sand samples with mean grain sizes approximating the above average values 

 exhibit about IC^ (by number) of heavy minerals and 2% or less of rock 

 or shell fragments. Thus, the beach is composed largely of medium to fine 

 quartz sand. Small samples of the average sand of the beach exhibit rel- 

 atively low Reynolds numbers under average temperature and salinity con- 

 ditions of the seawater. 



Tides at Virginia Beach are of the semi-diunal (equal) type and 

 have a mean range of 3'0 feet, as against a spring range of 3-6 feet. 

 Tidal currents in the study area are related to the ebb and flood through 

 the entrance to Chesapeake Bay. They are generally reversing in nature, 

 and are usually parallel to the shore. Harrison, Brehmer, and Stone 

 (I96U, fig. h) present evidence from which it may be calculated that peak 

 tidal-current velocities seme 3,000 feet from shore and a few feet above 

 the bottom do not exceed roughly 0.5 knot (O.85 ft /sec) in the study area. 

 Peak velocities measured one meter above the bottom at the end of the 15th 

 Street fishing pier (fig. IC, "northern transect") approximated 0.68 ft/ 

 sec. This pier marks the northern terminus of the study strip, and it 

 is here that the tidal currents are at a maximum for the study area. 



The wave climate for the study area may be estimated from an 

 analysis by Harrison of foiir years of wave records from a stepped-resis- 

 tance wave gage (fig. IB) maintained by the U. S. Navy in 20 feet of water 

 off Cape Henry and from five years of wave observations at Chesapeake 

 Lightship (fig. lA), in 60 feet of water. The brief summary that follows 

 indicates that roughly two-thirds of the waves that could be expected to 

 strike Virginia Beach come from only three directions and that mean heights 



