description of incipient motion predicts the seaward edge of the 

 initial profile modification within 3 percent for the waves tested, 

 Hcwever, the "null" condition or equilibrium condition of established 

 sediment motion was found to predict slopes up to 200 percent too 

 large. The beach shape is qualitatively correct in the offshore 

 region, hcwever, and the cause for the discrepancy may be in the de- 

 termination of the mass transport velocity distribution within the 

 bottom boundary layer. 



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

 Mechanics of Sand Movement by Waves . 



Certain additional data on the velocity pattern near the bed were 

 obtained with the modified pitot tube. Additional measurements to 

 determine the phase shift constant were also made by taking motion 

 pictures of injected dye. A report describing the motion in the boundeiry 

 layer near an oscillating plate for the general case has been initiated. 

 This contract was expanded to cover also the mechanism of sand movement 

 by wind. As a part of this portion of the study, various types of s«ind 

 traps have been calibrated in a wind tunnel, and efficiencies of these 

 various types checked and compared with each other. Five types of sand 

 trap were tested, three of the vertical type and two of the horizontal 

 type. So far only a single grain size has been tested, but tests are 

 planned with other grain sizes to study its effect on sand trap effi- 

 ciency and on amount of sediment transported. 



IV. University of California, Contract DA-49-055-eng-31. Wind Action 

 Over Shallow Water . 



This contract was completed with the preparation of a report 

 receiving limited distribution "Transient Wind Tides in Shallow Water", 

 University of California Institute of Engineering Research Technical 

 Report, Series 731, Issue 11. This report is concerned with the 

 surface time history of wind tide conditions, and the transient water 

 motion. It indicates that the water surface set-up may overshoot its 

 steady state value by a factor of 2, being then damped to the steady 

 state condition. 



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

 Study of Wave Refraction . 



A theoretical study was completed on the effect of frictional 

 resistzmce as a long wave propagates into or through a channel of 

 gradually varying cross-section. This report was published as 

 Technical Memorandum No. 112 of the Board. The work was required in 

 order to enable subtraction of effect of frictional resistance in 

 making studies of long waves, such as tsunamis, refracting over sub- 

 marine canyons. It is also applicable to the propagation of tidal waves 

 through inlet areas. Studies on secondary formation of multiple crests 

 from a single wave crest as a wave moves into and over shoal water 



37 



