Results (not presented) of our attempts to test equation 24 for its 

 applicability for prediction of swash-backwash slopes met with only limited 

 success when the computed slopes were compared to those actually observed. 

 Factors such as lift forces exerted on the grains due to groundwater move- 

 ment through the foreshore face and the imprecision of the measurement 

 techniques, may have contributed heavily to the inability to find a good 

 correlation between observed and computed slopes. 



Beach Model Comparisons 



Miller and Zeigler (1958) developed a model relating dynamics and 

 sediment patterns in the regions of shoaling waves, breaking waves, and 

 the swash-backwash' zone. Their model, based on theoretical considerations 

 and published experimental results, was intended to hold for these dynamic 

 zones "in a state of equilibrium." Miller and Zeigler's trend maps (1958, 

 Figure 22) for median sediment size and for sorting throughout the three 

 dynamic zones showed the trends summarized in Table 8. Also summarized in 

 this table are the observed trends of this study (based on Figures 7, 8, 

 and 9). 



Table 8 indicates rather poor correlation between model and observed 

 trends, the best correlation coming between predicted and observed median 

 (mean) size in the breaker zone. Special effects, such as outflow of 

 Rudee Inlet current at 3rd Street (Figure 1) and the presence of numerous 

 pilings at the landward ends of the 3rd and 15th Street pier transects may 

 have adversely influenced this comparison in three places. Still, the 

 comparison is rather poor. 



A further comparison of the observed trends for the swash-backwash 

 zone, with the model trends of Miller and Zeigler's (1958) "foreshore" 

 zone, shows that after backwash, observed sorting becomes poorer in the 

 seaward direction. The model predicts improved sorting. Observations 

 (Table 5, Figure 2) indicate an increase in mean size toward the sea in 

 the swash-backwash zone, and this was predicted by the model. 



SUMMARY REMARKS 



It was the main purpose of this paper to attempt a description of the 

 dynamic and related properties of the immersed beach sediment grains under 

 the conditions prevailing at the time of sampling. An extension of the 

 description over the range of expectable kinematic viscosities of sea water 

 at Virginia Beach (Table 7) can be accomplished from the tabulated values 

 of this report. 



The calculations of Reynolds number involved the density and dynamic 

 viscosity of Virginia Beach ocean water of 26.74 o/oo salinity at a 

 temperature of 6.9° C. and the settling velocity of the particles of a 



18 



