(d) Laboratory Study on Relation of the Littoral Drift Rate to 

 Incident Waves. 



A series of additional laboratory tests were made in the Shore 

 Processes Test Basin to obtain further data on the relation of rate of 

 littoral movement to incident wave characteristics. A few additional 

 tests were made on the 1 to 20 slope, before remodeling to a 1 to 10 

 slope to permit faster accumulation of data on this one slope. Most of 

 this year's tests therefore have involved the 1 to 10 slope. Tests in- 

 volving different lengths of beach have indicated that a beach length of 

 about 40 feet is sufficient, for the range of values being tested, to 

 eliminate any effect due to beach length. Accordingly most of the tests 

 made this year, and those planned for the future, will be made with these 

 shorter beaches; the shorter beach length enables somewhat more rapid 

 testing, and considerably easier handling. Most of the tests have utilized 

 a higher wave energy level than previously, with a maximum rate of trans- 

 port during this period being about 7,500 pounds (dry weight) per hour 

 with approximately 6-inch waves. Tests planned involve 8 to 9-inch waves, 

 and yet higher rates of sand movement are expected. A report discussing 

 the work of the previous several years was presented at the October 1959 

 American Society of Civil Engineers' meeting in Washington, and this oral 

 report is being put into a form suitable for publication, A further 

 report discussing the results of the testing since that time is also in 

 preparation. Work has also been carried out attempting to relate measured 

 net quantities of littoral accumulation at several points on the east 

 coast to wave energy derived from statistical hindcast wave data. 



(e) Measurement of Suspended Material in Laboratory Wave Tanks. 



Certain additional suspended sediment samples were obtained in a 

 small laboratory flume and in the wave basin in conjunction with tests 

 on littoral movement. In addition a series of samples has been gathered 

 in a wave flume using lower specific gravity crushed coal rather than 

 sand. It is hoped that these latter measurements may aid in defining 

 scale relations between model and prototype measurements. For this 

 purpose, they will be compared with measurements of material in suspension. 



(f) Wave Theory. 



Work has continued on basic wave theory with particular emphasis on 

 the determination of design wave criteria. A report "Wave Variability and 

 Wave Spectra for Wind -Gene rated Gravity Waves" has been published as 

 Technical Memorandum No. 118 of the Board. A number of wave records from 

 a wide variety of locations were subjected to a statistical analysis and 

 distribution functions of wave heights and periods derived. If the wave 

 length is regarded as proportional to the wave period squared (as assumed 

 in this report) length distribution functions may also be derived. The 

 joint distribution relationships between length or period and the wave 

 heights have also been obtained. Following these distribution functions, 



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