the zones between the high-tide line and -15 feet mean lower low water. 

 Because of these differences, tracing surveys confined solely to the 

 foreshore or offshore zone produce data only partially indicative of 

 transport in the zone of immediate concern to coastal engineers. The 

 indicated differing rates of transport, coupled with different depths 

 of sediment movement, add complexities to the realistic determination 

 of quantities of sediment movement. Observed patterns of sediment move- 

 ment indicate that previously used methods for solving the problem of 

 volume sediment transport, such as displacement of the center of gravity 

 of the tagged mass, simple dispersion models and random walk models, are 

 not adequate. While an accurate determination of sediment drift volume 

 remains illusive, qualitative data on sediment movement useful for 

 engineering purposes can be obtained on a scale heretofore unattainable. 

 Data obtained with the RIST system can be treated as synoptic observa- 

 tions of sediment transport in several adjacent environments. Qualita- 

 tive sediment transport data of the type now possible to obtain through 

 RIST have application in the studies of such engineering works as: 

 (1) the behavior of a groin; (2) the functioning of a "weir-jetty", 

 and (3) shoaling harbors. 



Research and development toward improving the RIST program continue, 

 including improvement of data handling programs, quantification of drift 

 measurements, and field tests on other sites. All are designed to make 

 the system a more efficient engineering and research tool. 



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