96 



Figure 5-1 . SCUBA-equipped diver with bag holding tracer samples 



pie runs when there was an abrupt change in the wave parameters required by 

 other SUPERTANK participants. 



The surf zone tracer experiments are summarized in Table 5-2. Tracer 

 injected on the subaqueous portion of the profile, such as on the berm, was 

 observed visually. Qualitative descriptions of tracer movement from the visu- 

 al observation are not discussed further here. 



All sand samples from the tracer experiments were air-dried and inspected 

 for tracer content using an ultraviolet light in a dark room. Samples contain- 

 ing a large amount of tracer were reduced with a sample splitter to render 

 counting of tagged grains a manageable task. Weighed samples or splits were 

 spread to one-grain thickness on a flat-black surface for counting. This proce- 

 dure yields the number of tracer grains in the measured weight of the sample, 

 which can then be used to calculate the concentration in terms of tracer grains 

 per gram of sample, to place all samples on the same basis for comparisons. 



Data Analysis 



Tracer concentrations for the offshore sample runs are listed in Table 5-3. 

 Station numbers refer to local grid position with respect to the injection line 

 (0.0), with positive and negative numbers respectively signifying offshore and 

 onshore directions. Magnitudes of the station numbers denote distance in me- 



Chapter 5 Tracer Measurements of Sand Dispersion 



