PROGRESS REPORTS ON RESEARCH SPONSORED BY 

 THE BEACH EROSION BOARD 



Summaries of progress made during the past year on the several 

 research contracts in force between universities or other institutions 

 and the Beach Erosion Board, together with brief statements as to the 

 status of some research projects being prosecuted in the laboratory of 

 the Beach Erosion Board, are presented below. These summaries supple- 

 ment and continue those contained in prior issues of the Bulletin. 



I. University of California (Scripps Institute of Oceanography) 

 Contract DA-49-005-eng-3.' Principal investigator - D. L. Inman 



The measurement of sand-level changes by underwater observation 

 of reference rods imbedded in the sand bottom were continued. The 

 total range of sand level at the 18-foot depth station probably exceeded 

 2 feet, though the reference rods were lost after changes in excess of 

 0.6 foot were measured. Maximum changes of 0.29, 0.16, and 0.15 foot 

 were measured at stations where the depth was 30, 52, and 70 feet 

 respectively. Significant monthly and seasonal changes occurred. 

 Accuracy of the measurements was stated to be on the order of ±0.05 

 foot as compared to ±| foot obtained by sonic sounding over the same 

 area. A report by Inman and Rusnak, "Changes in Sand Level On The 

 Beach and Shelf at Ja Jolla" has been issued as Technical Memorandum 

 No. 82 of the Board. 



A final report on the orbital velocity measurements, by Inman 

 and Nasu, was prepared as Technical Memorandum No. 79 of the Board, 

 Orbital velocities just seaward of the breaker zone were measured 

 simultaneously with wave pressure records. The observed maximum 

 horizontal velocities were compared with those predicted from solitary 

 wave theory. The agreement was better for longer period waves, but 

 is generally favorable when the ratio of wave height to water depth 

 is greater than about 0.4. 



Additional data wese gathered describing the physical aspects of 

 ripples generated by shallow water waves. The data indicate that 

 the wave length of the ripples is proportional to the horizontal 

 diameter of the orbit of a water particle near the bottom, when the 

 orbit diameter is less than a limiting value determined by the size 

 of the sand. A report is presently in preparation. 



This contract was terminated in March 1956. 



II. University of California, Contract DA-49-005-eng-8. Principal 

 Investigator, P. D. Trask 



Seasonal sampling of the Pt. Reyes beach has continued, the beach 

 now having been occupied 12 times since June 1953. The sampling has 



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