however, was done only in the two sections of the tank containing the 

 finer sized sediments. Figure 3 shows the size distribution curves 

 of the 0.22-mra. and 0.47-mm. sediments. The wave tank was provided 

 with a bridge-type carriage spanning the tank width and equipped with 

 rollers for convenient movement to any desired sampling location along 

 the tank. The entire sampling apparatus was mounted on the tank 

 carriage making it possible to conveniently position the intake 

 nozzle at any desired sampling location. Waves were produced by a 

 curved-face bulkhead type generator moving through a forward and 

 backward rolling motion made possible by the use of an eccentric 

 drive (Figure 2). Wave heights and thus wave steepness ratios could 

 be varied by adjustment of the eccentric setting. The generator 

 was powered by a vari-drive motor permitting a wave period range of 

 0.9 to 3.5 seconds. 



Depth and Sampling Elevation Measurements. It was desired to keep 

 the depth a.s nearly constant as possible during the actual pumping 

 operation; hence prior to sampling an equilibrium profile was allowed 

 to form for the wave conditions tested. Despite this, however, due 

 to the wave action the bottom configuration was constantly changing 

 with time, primarily due to ripple formation and movement. This 

 bottom ripple movement resulted in a changing depth at any point which, 

 though slight, was still significant. It was thus necessary to deter- 

 mine an average depth, taking into account the bottom changes as 

 evidenced by the elevation change of a given ripple crest or trough 

 during the pumping of a sample (Table 1, Column 1). The actual average 

 depth for a given instant was then determined as (hV2) + E where hu 

 was the ripple height (trough to crest) and E was the vertical distance 

 from the ripple crest to still water level. The tabulated depths 

 however, reflect the average of two values of the quantity, (hp/2 ) + E, 

 one taken before starting the sampling and a second one approximately 

 five minutes later, after completion of sampling. 



The necessary measurements to determine depth, sampling elevation 

 above bottom and still water level were made using a vertically oriented 

 point gage with a vernier scale mounted to the wave tank carriage 

 (Figure 4). A similar type vernier scale was used to measure the height 

 of the nozzle above bottom. 



Wave Measurements. A high speed pen-and-ink Brush oscillograph and 

 a parallel wire resistance wave gage were utilized for recording the 

 pertinent wave data. A continuous wave record was obtained covering 

 each sampling period. The wave recording equipment was calibrated be- 

 fore each series of sample collections and the calibration checked at 

 the end of the sampling series. Average wave heights were determined 

 from the wave record for each sampling, and the wave height thus 

 determined for a particular sampling was the wave height used in 

 summarizing the results. Figure 4 also illustrates the wave height 

 measuring and recording equipment schematically. 



44 



