In addition, data obtained partially in conjunction with this con- 

 tract, on the use of naturally radioactive thorium in beach sands as a 

 means of detecting the direction of littoral drift, was used in a report 

 "Transportation of Coastal Sediments" and given limited distribution by 

 the University of California as Institute of Engineering Research Technical 

 Report, Series 185, Issue 1. It is being published as Technical Memorandum 

 No. 131 of the Beach Erosion Board under the title "Littoral Studies Near 

 San Francisco Using Tracer Techniques". 



II. Massachusetts Institute of Technology, Contract DA-49-055-eng-16. 

 Sorting of Beach Sand by Waves . 



Work has proceeded in both an experimental and a theoretical direction 

 toward the determination of dissipation of wave energy in the breaker region 

 and the generation of longshore currents. The experimental program has been 

 primarily concerned with the development of an adequate orbital velocity 

 probe, utilizing a thermistor. The theoretical program has proceeded toward 

 obtaining equations for the orbital velocities and particle displacements 

 in very shallow water and the breaker region, initially using the work of 

 Biesel. His development has been extended to higher order terms in wave am- 

 plitude in order to introduce the effect of mass transport. It is planned 

 to program the resulting formulae on a computer to yield the appropriate 

 wave parameters as functions of depth, distance, and beach slope. 



III. University of California Contract DA-49-055-eng-17. Fundamental 

 Mechanics of Sand Movement by Waves . 



A report "A General Reconnaissance of Coastal Dunes in California" was 

 completed and published as Miscellaneous Paper No. 1-62 of the Beach Erosion 

 Board. This report describes the dune localities along the California Coast, 

 and examines their common features. Dune forms, beach configuration and 

 condition, activity of dune sand, and sediment sources are the factors 

 considered in describing the localities. Experiments were conducted in a 

 4x4xl00-foot wind channel in which the performance of the portable sand trap 

 developed previously was compared with the total transport obtained by a 

 trap at the end of the channel. 



Further theoretical work has been carried out on sediment transport by 

 wave action using, initially, a statistical approach. The two parameters 

 describing flow intensity and sediment rate respectively were determined 

 independently, but their functional relationship include constants which 

 can be determined only by experiment. Data obtained previously by Manohar 

 have been explored for this determination, but indicate that additional 

 experimental data are required. 



TV. University of California, Contract DA-49-055-eng-44. Laboratory Study 

 Of Wave Refraction 



Additional work was done in the ripple tank on the Mach stem reflec- 

 tion phenomenon, using concave barriers with wavy and roughened surfaces. 



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