where 



Rq = burial depth ratio 



R^ = corrected count rate (c/s) in RAD Channel 1 



R2 = corrected count rate (c/s) in RAD Channel 2 



Rj and R2 represent an average of 10 readings. On the beach face, com- 

 puted ratios indicate burial with time on the injection line. Laterally 

 along the beach face, ratios indicate sand is nearer the surface as 

 distance from the injection line increases. Seaward of the surf zone, 

 little lateral change in ratios was detected, although an increase -in 

 ratios occurred through time. Interpretation is that mixing to some 

 depth has occurred, rather than stratification with an overburden of 

 dead sand. 



5. Results of Gold Experiments 



A comparison of maps showing the distribution of xenon- and 

 gold-tagged sand (Figures 11 and 12, and 16 through 21) indicates dif- 

 ferences in areal extent and possible interpretive differences. Some 

 differences in grain size of tagged sand was noted in a previous section 

 of this paper. As the size characteristics were still similar to the 

 untagged sand in the study area, no deleterious effects are judged to 

 have occurred because of tagging techniques. Tests at ORNL (Stephens, 

 et al., 1969) indicate their tagging techniques firmly fix the radio- 

 active gold to the grain surface. The maps are therefore judged to 

 represent dispersion of sand grains and not the dispersion of gold 

 abraded or leached from the surface of sand grains. 



Differences in ocean conditions during the xenon and gold experiments 

 might be the cause of the different patterns of movement suggested by the 

 maps. However, during the first days of the gold experiment, sea, swell, 

 and longshore currents were closely similar to those during the xenon 

 experiment. During 6, 7, and 8 October, wind and swell were considerably 

 higher than any conditions encountered during the earlier xenon tests. 



Gamma photons emitted by gold are much greater than xenon in energy 

 (0.4 million electron volts versus 0.08 million electron volts). There- 

 fore, they are more easily detected, even in smaller grain concentrations, 

 than xenon-tagged sand. It is the consensus of the field- program partic- 

 ipants that the data used in compiling maps depicting movement of gold- 

 tagged sand are real, and that for purposes of working in the ocean 

 environment on a large scale, gold-tagged sand yields better information 

 than sand labeled with xenon using present tagging techniques. 



An experiment in the CERC SPTB to study littoral drift indicated 

 rapid alongshore movement at the landward edge of the breaker zone, and 



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