shallow water. An inclosed wave flume equipped with a suitable blower 

 is the basic piece of equipment being used for the study. The Beach Erosion 

 Board and the Jacksonville District, Corps of Engineers, are joint sponsors 

 of this contract. 



The laboratory flume used in this study was constructed at University 

 expense prior to the date at which work on the contract was permitted (2 August 

 1953) . Most of the work during the first two months was devoted to install- 

 ing instruments for measuring waves, wind, pressure drop, and wind tide. 



Tests to date have been concerned with the calibration of instruments 

 and preliminary runs with smooth walls. Some study also has been given to 

 the type of roughness that might be used to give an ultra-rough bed in sub- 

 sequent tests. 



IV. Scripps Institution of Oceanography, Quarterly Progress Report 

 No. 17, Contract No. »J-U9-055-eng-3, July-Sept. 1953 . 



Analyses of orbital velocity data show that the observed horizontal 

 orbital velocities compare favorably with velocities predicted from solitary 

 wave theory when: l) the w ave profile is not complex , and (2) the relative 

 wave height H/h is greater than about O.U. The agreement with wave theory 

 is somewhat better for long period waves than for short period waves, but in 

 general is still quite good for wave groups with significant periods as short 

 as about 6 seconds. 



Seven months of observing reference rods by divers using self-contained 

 diving gear have shown rapid and extensive changes in shallow water (6 ft.), 

 with much less change of sand level in greater depths (30 to 70 ft.). A new 

 series of reference rods was placed, during September, at 20-ft. intervals 

 along a profile extending through the surf zone and onto the beach foreshore. 

 The purpose is to obtain accurate measurements through the surf zone. 



Because of the important role ripples play in the mechanics of sand 

 transport by wave action, a systematic program of measurement and ripple 

 study has been initiated. Ripples are photographed and measured in con- 

 junction with the reference rod studies. Ripples have always been found 

 to be present when the significant orbital velocities exceed approximately 

 0.3 ft. /sec. (for sand with a median diameter of about 0.12 mm,). In 

 general, the type of ripple is related to the nature of the orbital dis- 

 placement and velocity. The form of the ripple profile tends to imitate in 

 miniature the form of the profile of the generating surface wave above it. 

 In deep water, where the wave profile is trochoidal, the ripple is tro- 

 choidal; in shallow water, where wave forms are solitary, ripples consist 

 of isolated crests separated by flat troughs. Further studies are planned; 

 and understanding of the mechanism of sand movement in relation to ripple 

 regime may aid in explaining some of the apparent anomalies between sand 

 transport and the rigor of wave action. 



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