ABSTRACT 



The purpose of the ^Radioisotopic _Sand Tracer CRIST) study is to 

 develop and use radioactive tracer methods for research in sand movement 

 and littoral processes. Research objectives include determination of 

 suitable radioactive isotopes, development of mobile and stationary radi- 

 ation detectors, and development of suitable handling and survey programs. 

 Concurrent with these objectives, studies of sediment transport around 

 the Point Conception headland and of the mechanics of littoral transport 

 are being conducted. Methods developed by this program have direct appli- 

 cation to engineering design of such works as harbor development and beach 

 erosion prevention, and quasi-military application such as the location 

 of radioactive or other toxic materials . 



To date, sand grains indigenous to the study area have been labeled 

 with xenon-133 which does not adversely affect the hydraulic properties 

 of the sand. Various devices and methods of employing the tagged sand 

 have been studied. A mobile detector system using cesium iodide crystals 

 and housed in a "ball" towed behind an amphibious vehicle detects the 

 quantity and areas of radiation. Computer programs have been developed 

 to correct and plot radiation data. 



A field test of equipment and principles at Cape Kennedy, Florida, 

 was successful. Additional field tests were at Surf and Point Conception, 

 California. These tests included isotope distribution, sediment analysis, 

 offshore profiles, and oceanic and atmospheric environment monitoring. 

 In addition, model tests were conducted in the Shore Processes Test Basin 

 at the Coastal Engineering Research Center (CERC) to compare high and low 

 specific activity xenon, and to study beach development and movement under 

 the controlled conditions of a hydraulic laboratory. 



The data density is sufficient to support tentative conclusions 

 regarding offshore sediment movement in the Point Conception area. 

 Additional field tests will extend the survey from the beach through the 

 surf zone. In addition, development of instruments and field programs 

 will continue in order to permit their routine use by technicians and 

 field crews. 



FOREWORD 



For 35 years the U. S. Army Corps of Engineers' Coastal Engineering 

 Research Center (CERC) and its predecessor, the Beach Erosion Board, have 

 been studying coastal phenomena. While -interest at CERC extends from 

 wave generation in the deep ocean to the original source of sediment at 

 the headwaters of streams in the high mountains, the practical limitation 

 of its work is the coastal area. The coastal area can be considered to 

 extend from the bluffs or sand dunes immediately landward from the present 

 position of the shoreline to water depths representing the outer limit of 

 bottom material movement by wave action. 



