The movement of contoiars at the five ranges for elevations of -0.9, 

 -1.2, and -2.1 feet is compared in Figure 31. The lateral variation in 

 the movement of the offshore zone is quite noticeable at -1.2 and -2ol 

 feet; e.g., the positions of the -2 = 1-foot contour at 335 hours are sta- 

 tions 25.6, 26.3, 27.0, 27.2, and 27.5 feet along ranges 1, 3, 5, 7, and 

 9, respectively. 



The offshore slope, measured between the -0.9- and -2.1-foot contours, 

 varied from 0.113 along range 1 to 0.098 along range 9. 



c. Profile Adjustment Under 3.75-Second Wave . For 375 hours, the 

 profile in experiment 71Y-06 was attacked by a fairly steep (H^/L^ = 

 0.021) wave. Then, for the next 5 hours, the profile was subjected to 

 a low (Hq/Lq = 0.002) wave. As expected, this low wave moved sediment 

 back toward the shoreline and onto the foreshore. The profiles along 

 range 3 at the beginning and the end of this subexperiment are compared 

 in Figure 32. The low wave flattened out the many small bars and troughs 

 within the inshore zone and deposited material on the foreshore. Move- 

 ment of the seawardmost contour intercepts during the 5-hour period is 

 plotted in Figures 33, 34, and 35. These plots indicate deposition at 

 elevations 0.2, 0.1, 0, -0.1, -0.2, and -0.5 foot, and erosion at eleva- 

 tions -0.3, -0.4, -0.6, -0.7, and -0.8 foot. A photo in Figure 36 shows 

 deposition on the foreshore zone at 380 hours. After the experiment was 

 stopped, a trench was dug along the middle of the test area. The light- 

 toned sediment on top in the photo is the deposition during the 5 hours 

 of long-period waves. 



3. Sediment-Size Distribution . 



The sand for these experiments was the same sand used by Savage (1959, 

 1962) and Fairchild (1970a, 1970b). Because the samples collected in this 

 study were surface samples, and therefore subject to winnowing action, the 

 median grain size may have been slightly less when Savage and Fairchild 

 performed their tests. The data reported here are the Rapid Sediment 

 Analyzer (RSA) values, which were generally 0.04 millimeter greater than 

 that determined by the dry sieve method (see Vol. I). The RSA values are 

 used here only because all the data were reduced by this method. 



Tables 10 and 11 give the sediment-size analysis results from experi- 

 ments 71Y-06 and 71Y-10. Sediment samples were collected along the pro- 

 file before the beginning of experiment 71Y-06, and the results of the 

 size analysis are given in Table 10. The average median grain size was 

 0.27 millimeter, which is assiamed to represent the median grain size, 

 dsoj for the unsorted sediment in both experiments. 



a. Experiment 71Y-06 . A summary of the median grain sizes for ex- 

 periment 71Y-06, including the mean of the medians, range of values, and 

 the number of samples within each profile zone for each time, is given in 

 Table 12. The median grain size on the foreshore remained above 0.27 

 millimeter (with one exception). This value of 0.27 was the same as the 

 mean of the medians of all san^jles from the beach at hours. The increase 



64 



