RADIOISOTOPIC SAND TRACER STUDY, POINT CONCEPTION, CALIFORNIA 



Preliminary Report on Accomplishments 

 July 1966 - June 1968 



Section I. PROGRAM 



1. Introduction 



In 1966 the U. S. Army Corps of Engineers' Coastal Engineering Re- 

 search Center in cooperation with the Atomic Energy Commission, initiated 

 a 3-year Radioisotopic Sand Tracer Investigation of Littoral Transport 

 around Point Conception, California. Program objectives may be summarized 

 as: a) a study and selection of suitable radioisotope(s ) ; b) development 

 of radiation detection equipment capable of operating in the beach and 

 marine environment to depths of 100 feet; and c) trace movement of tagged 

 sand in a coastal zone. A major part of the development of hardware and 

 tagging techniques has been performed by AEC's Oak Ridge National Labora- 

 tory at Oak Ridge, Tennessee. Other direct participants in the study are 

 U. S. Navy, U. S. Air Force, Corps of Engineers District Office in Los 

 Angeles, National Aeronautics and Space Administration, and the State of 

 California. Recognizing the potential, broader geographic applications 

 of this 3-year minimum research and development program, the rather pon- 

 derous official title has been shortened to Radioisotopic Sand Tracer 

 Study with the acronym RIST. 



Sediment in the littoral environment moves in response to various 

 complex processes. In the nearshore zone (that zone extending from the 

 water line to the limit of nearshore currents at about 50-foot depths) 

 waves approaching at an angle generate currents that move in response 

 to the direction of wave approach. Because more than one wave train may 

 impinge upon the shore at the same time, more than one current direction 

 and velocity maxima may exist. Further, in any given wave a water particle 

 circumscribes a circular or elliptical orbit for which two additional 

 velocity maxima exist opposed by 180 degrees. These and other factors 

 enter into the problem, and may be classified as force and response 

 elements. Examples of force elements are wave height and period, angle 

 of wave approach, and stage of the tide; several response elements are 

 particle size distribution of the sediments, density of the particles, 

 and bottom and beach slope. The interaction of the force and response 

 elements causes a continual action and reaction effect. Problems of the 

 littoral zone, therefore, are concerned with many factors which may vary 

 widely and which interact with each other singly and in combination in 

 a most complicated manner. 



The responses to the expenditure of energy by waves, currents, and 

 other forces upon a sandy coast are erosion and transportation of the 

 sedimentary particles. Because many of the shores of the United States 

 and the world are sandy, investigators at CERC and other laboratories 



