average is an average of sample averages, each sample average representing 

 conditions at a different profile line. For sample set A, the sample mean 

 is the value obtained from equation (2), but for sample set B, the sample 

 mean is the median given by the improved RSA program. For all practical 

 purposes, the mean and the median of sand samples in this study are 

 identical. 



III. RESULTS 



1. Sand-Size Distribution . 



Tables 2 and 3 summarize the sample means of sample set A, with sample 

 averages and profile averages given by profile line, elevation, and month 

 of sample collection. Tables 4 and 5 are similar summaries for the RSA 

 means of sample set B. Table 6 compares McMaster's (1954) results with 

 results from sample set A for both the sample averages of the RSA means 

 and the sample averages of sample means. 



Figures 15 to 18 are plots of sample set A only (data from Tables 2 

 and 3) . Sample averages are plotted against relative profile location in 

 Figure 15 to illustrate the geographic distribution of mean sand size on 

 southern New Jersey beaches. The distribution of mean size with elevation 

 is illustrated first in Figure 16 as sample averages and then in Figure 

 17 as profile averages. Finally, the variation of mean sand size with 

 time is shown in Figure 18 as sample averages by month. 



2. Sample Mean versus Slope . 



The sample means of all samples whose elevation was less than MHW are 

 plotted against the slope of the sample site in Figure 19. The slopes 

 were calculated from the survey data by the CERC computer program PRSEG. 

 The solid line in Figure 19 is equivalent to the New Jersey-North 

 Carolina curve on Figure 4-33 of the Shore Protection Manual (U.S. Army, 

 Corps of Engineers, Coastal Engineering Research Center, 1975). 



IV. DISCUSSION OF SAMPLE SET A 



1. Magnitude of Size Variation . 



The range of variation in mean sand size by profile, at the three 

 localities studied, is from 1.55 phi (0.34 millimeter) at profile line 12 

 on Long Beach Island to 2.30 phi (0.20 millimeter) at profile line 10 on 

 Ludlam Island (Fig. 15). The size difference between 0.20 and 0.34 milli- 

 meter has a coastal engineering significance in its effect on beach shape, 

 slope, and width. Fall velocity of 0.34-millimeter sand is double that 

 of 0.20-millimeter sand (U.S. Army, Corps of Engineers, Coastal Engineer- 

 ing Research Center, 1975, p. 4-84) which can result in the finer sand 

 having a barred profile and the coarser sand having a profile with a prom- 

 inent berm (U.S.. Army, Corps of Engineers, Coastal Engineering Research 

 Center, 1975, p. 4-81). According to Bascom (1951), 0.34-millimeter sand 



35 



