indicate burial at the updrift end of the radioactive mass; particles 

 released from these zones therefore would be few in number, and by down- 

 drift dilution with untagged sand could escape detection. A relative 

 rate of alongshore transport would be: inshore zone > beach face > off- 

 shore zone seaward of peaking and breaking waves. Sea and swell during 

 the October series of experiments are summarized in Figure 23. 



Mathematical simulation studies presently underway as part of the 

 RIST program tend to fit the data observed in the field (W. R. James, 

 personal communication) . The observed difference in transport velocity 

 is in direct agreement with the model tests conducted by Taney (1963) 

 and the results of field studies reported by Ingle (1966) . Studies by 

 Komar (1969), which were confined to the beach face, imply greater 

 velocity of sediment transport in the inshore zone than on the beach 

 face. 



In any sand-tracing experiment, knowledge of the depth and pattern 

 of sand burial is important; it is fundamental to quantify littoral trans- 

 port. Courtois and Sauzay (1966) present several theoretical models that, 

 in general, follow a parabolic law and assume mixing (contrary to strati- 

 fication) of the tagged sand with untagged "dead" sand. However, ex- 

 perimental results obtained in a later study (Courtois and Monaco, 1969) 

 indicate burial offshore more closely follows an exponential law, and 

 that stratification exists. Komar' s (1969) beach studies (using fluores- 

 cent dyed sand) suggest an exponential type of burial law; that is, the 

 depth of burial decreases exponentially with downdrift distance from the 

 point of injection. 



Short cores from the beach face obtained in this RIST experiment 

 indicate stratification occurred, and tagged sand was overlain by dead 

 sand. Core data is insufficient to contribute additional confirmation 

 to the decrease in burial depth downdrift from a source. Ratios of the 

 peak heights of the two radiation channels do tend to confirm a decrease 

 in burial downdrift. Calibration of the detector system is still in- 

 complete, so precise information about burial depth is still unknown. 

 However, where count rate is of the same order of magnitude, computed 

 ratios indicate decreasing depth of burial on the beach face with in- 

 creasing distance from the source. Offshore, seaward of the outer line 

 of breakers, the ratios are not significantly different, and this is now 

 interpreted to mean little burial by "dead" sand, or at least shallow 

 burial with mixing of tagged and untagged sand. Bed forms offshore in 

 this area are slight ripples of sand overlying a firm sand bottom and 

 are consistent with such an interpretation. Partially destroyed large 

 ripples (6 by 4 by 1 1/2 feet deep) were also observed in the zone from 

 -16 feet mean lower low water to the limit of observations at -20 feet 

 mean lower low water. Waves and currents creating those features would 

 be expected to cause deep burial and a consequent change in the radiation 

 ratios. 



During February 1969, another,, field test at Surf, California, was 

 undertaken. The specific purpose was to obtain data on the pattern of 



35 



