at Virginia Beach, taken by the U. S. Coast and Geodetic Survey (C. Taylor, 

 1963, oral communication), and (2) the mean value for wave period and the 

 first mode for the distribution of wave heights for 5 years' running 

 records of waves made at the U. S. Navy's Cape Henry wave gage. The 

 average values of 5.3 seconds (for wave period) and 2.0 feet (for wave 

 height) were determined by the significant height method of analysis. 

 Mean water depth at the wave gage approximated 18 feet. The mean values 

 (Table 7) for temperature, salinity, and kinematic viscosity at Virginia 

 Beach are 56.8° F. , 25.7 o/oo and 1.3 x lCr^f t^/sec . Expectable upper and 

 lower limits to these ranges are given in Table 7. 



On the basis of several theoretical and laboratory studies, Eagleson, 

 et al. (1963) developed an equation for the determination of the size of 

 grains (D e ) in oscillating equilibrium on a sloping sand beach (neglecting 

 reflection coefficient) of the form: 



T 2 f (^ f /6 2/3 



D e = ! 131 TrT U - s f ) sina J |_ Tt J (23) 



o 



where 



D_, = sand grain diameter, in feet 

 H Q = wave height in deep water, in feet 

 V = kinematic viscosity of fluid (ft /sec) 

 L = wave length in deep water, in feet 

 g = gravitational constant, 32.2 ft. per sec 



s = specific gravity of fluid or sediment, as specified 



j. j. . . ,- , h . ctnh2 kh 

 ±i = a function fi ( T — ) = T - 



"O sinh^ kh + k h 



where: k = wave number = 2 tt/l 

 h = water depth 



a - beach slope 



Substitution of the values mentioned previously (into Equation 23) 

 gives a measure of the effects of varying particle sizes (expressed as 

 nominal diameters) and kinematic viscosities on beach slopes (Table 7) in 

 the shoaling-wave zone. The three particle sizes chosen for Table 7 would 

 correspond roughly to mean sizes of sand found: (1) offshore, within a few 

 miles of Virginia Beach (0.12 mm ), (2) in the dunes at Cape Henry and alonj; 

 Virginia Beach (Wentworth, 1930, Figures 112, 114, 115, and 116), and (3) 

 offshore 10 to 40 miles in restricted zones (M. N. Nichols, 1963, oral 



16 



