Swash-backwash Zone. Trends of values determined for the samples 

 taken in the swash-backwash zone (Figure 2) may be summarized as follows: 

 mean size--slow increase in seaward direction over upper half of zone, 

 rapid increase over lower half; sorting — best near landward side and in 

 upper half of zone, rapidly becomes poorer in seaward direction in lower 

 half of zone; Reynolds numbers under existing natural conditions (but for 

 infinite fluid) — slow increase in seaward direction over upper half of zone, 

 rapid increase over lower half. Limited data (Table 5) indicate that, for 

 a given uprush, the mean size and Reynolds number are greater at slack 

 water than after the backwash, on the upper five-sixths of the swash- 

 backwash surface. As would be expected from this finding, sorting (Table 

 5) is worst at slack water of the uprush. 



Mineralogy 



Table 2 presents data on the relative abundance of components other 

 than quartz grains found in the different sieve fractions of the mixed 

 Virginia Beach sands. Heavy minerals were significantly abundant only in 

 the residue fraction passing through the No. 230 sieve, while rock and 

 shell fragments were of greatest significance in the fraction larger than 

 2 mm. It should be noted here that these two fractions were found to be 

 a very small component of the mixture of sands both in numbers and in 

 weight. Nevertheless, the presence of rock and shell fragments in the 

 breaker zone is of great significance in the determination of size param- 

 eters and dynamic properties. Although the amount of sediment finer than 

 0.062 mm tends to increase offshore from the breaker zone, it can be 

 assumed that its significance remains small in analysis of size and 

 dynamic properties and may be considered negligible within the length of 

 our transects. Zeigler, et al. (1960), state that a monomineralic (i.e., 

 quartz) assemblage may be assumed when the quantity of heavy minerals is 

 small. 



Application of Data 



The importance of the values presented in this descriptive study to 

 the practical problems of beach nourishment and beach protection, and to 

 many academic problems relative to the erosion, transportation, and 

 deposition of sand, will come only when said values find their way into 

 mathematical expressions. The values herein reported are for only a 

 specific set of conditions. In order to demonstrate the possible use of 

 the values, some equations are presented and mean or extreme sea-state and 

 particle-characteristic values are substituted into them for illustrative 

 purposes. The first example (Table 7) shows the dependency of the slope 

 of the beach in the shoaling wave zone on particle and sea-state properties. 



The slope values of Table 7 are determined from the average mean 

 nominal-diameter values of Table 6 for the shoaling wave dynamic zone and 

 are based on; (1) the measured values of water temperature and salinity 



15 



