have studied sediment transport both in the laboratory and in the field. 

 Generally, such studies are made along a long, straight beach in order 

 to simplify the experiment. A much more complicated situation exists 

 where the shoreline undergoes a radical change in orientation. Point 

 Conception, California, is a geographic example of this condition. 

 (See Figure 2) . 



Point Conception and Government Point (as well as Point Arguello 

 and Pedernales Point to the north) are rocky promontories which extend 

 seaward from the general alignment of the shore. The shore is backed by 

 a sheer bluff rising approximately two hundred feet above the sea. The 

 nearshore bottom is rock interspersed with sandy areas. Part of the 

 nearshore bottom area appears to be swept free of sandy sediments; also 

 extensive kelp beds present in the area are generally indicative of a 

 rocky bottom. From general knowledge of the processes functioning in the 

 area, the littoral drift has been assumed by earlier investigators to 

 move from the north toward Point Conception and eastward away from it. 



Very little is known concerning littoral transport in the vicinity 

 of headlands or other supposed barriers to littoral drift, and Point 

 Conception is no exception. If the sedimentary particles comprising 

 this littoral drift do, in fact, move around the headland, the mechanics 

 of movement are unknown. Lateral movement could occur in shallow or 

 deep water or by a series of traverses essentially normal to the shore. 



2. Scope and Objectives 



The purpose of the Radioisotopic Sand Tracer Study (RIST) is to 

 develop and utilize radioactive tracer methods for research into sand 

 movement and littoral processes. Research objective include determina- 

 tion of suitable radioisotopes, development of mobile and stationary 

 radiation detectors, and development of suitable radioisotope handling 

 and survey programs. In conjunction with these objectives, studies of 

 sediment transport around the Point Conception headland and of the 

 mechanics of littoral transport are being conducted. 



Development of suitable methods for using radioactive tracers in 

 littoral transport studies required the accomplishment of the following 

 specific objectives: 



a. Study and selection of isotopes possessing a k- to 20-day half- 

 life, which emit y radiation with energy peaks of the different isotopes 

 sufficiently separated to permit detector discrimination in the field. 

 In addition, it is desirable that the isotope be biologically inert. 



b. Study of the isotopes selected to determine suitability of 

 labeling technique and compatability with the sediment being labeled. 



c. Design of a submersible radiation detection system using scin- 

 tillation detectors. At present, the system monitors a single isotope 



