3. Sediment-Size Distribution . 



The sand for these experiments was the same sand used by Savage 

 (1959, 1962) and Fairchild (1970). In Volumes II and III, the median 

 grain size (sieve method) for the material was reported to be 0.23 milli- 

 meter. The material added to the profile in this experiment for a 0.05 

 initial slope was evidently slightly finer. The six surface samples 

 collected from the profile before the start of the experiment and ana- 

 lyzed by the sieve method had a d5o of 0.22 millimeter. 



All samples collected for this experiment were analyzed by the Visual 

 Accumulation (VA) tube method and 10 percent of the samples were analyzed 

 by the dry sieve method for quality control (described in Vol. I). The 

 values given here are the VA tube results. In Volume I, results showed 

 that the VA tube median is 0.015 millimeter less than the sieve median 

 for the 10 percent of the samples analyzed by both methods. 



Table 9 gives the median grain-size results, including values at the 

 beginning of the experiment. The average hour median grain size was 

 0.21 millimeter. 



A summary of the median grain sizes, the mean of the medians, range of 

 values, and the number of samples within each profile zone are given in 

 Table 10. At 100 hours the foreshore was an eroding foreshore and the 

 median grain' sizes of the two samples were high. Median grain sizes 

 varied the most in the inshore zone. The values in the offshore zone 

 were all low, as would be expected in an area of deposition. However, 

 the mean of the medians was 0.21 millimeter in both the inshore and 

 offshore zones. 



At 180 hours (when twice as many samples were collected), the foreshore 

 no longer eroded but had built up with the deposition of finer material, 

 ranging from 0.20 to 0.22 millimeter. The inshore zone still had the 

 widest range of median sizes, but included more finer samples. The off- 

 shore zone had a wider range of median values, including some finer and 

 some coarser than the values at 100 hours. The mean of the medians was 

 0.21 millimeter in all three zones. 



4. Breaker Characteristics . 



A plot of breaker position superimposed on a plot of contour movement 

 along range 3 is shown in Figure 18. During the first 20 hours the wave 

 broke by plunging at depths between 0.6 and 0.7 foot. From 20 to 100 

 hours the breaker type varied between plunging and spilling and the wave 

 broke at depths varying from 0.6 to 0.7 foot. After 100 hours, the breaker 

 conditions were more complex. At the seaward end of the inshore zone the 

 wave broke (except at 105, 120, and 125 hours) by spilling at depths be- 

 tween 0.7 and 0.8 foot. At the shoreward end of the inshore zone, the 

 wave broke by plvmging at depths between 0.2 and 0.4 foot, except at 115 

 hours when it broke at a depth of 0.6 foot. 



38 



