In order to investigate this relation, measurements of the change 

 in ripple height were made and tabulated along with depth, sediment 

 concentration, wave height, etc. This data is also contained in Table 1. 

 Column 1 of Table 1 gives the changes in ripple height which is seen 

 to vary significantly, but in an apparently random fashion. The actual 

 ripple height changed as much as 0.035 foot (or 35% of its maximum 

 height of 0.1 foot) in roughly 100 seconds. 



The constantly changing ripple height, represented essentially a 

 constantly changing depth. This depth change imposed an interaction 

 between the bottom and -the turbulent fluid motion, which rendered 

 improbable the existence of a uniform pattern of sediment concentration. 

 Due to the random variation in magnitude and direction of the forces 

 accompanying the orbital currents and turbulent motion associated with 

 the wave action, the concentration pattern was very erratic and non- 

 uniform; that is, it exhibited a wide range of total suspended load, 

 which apparently followed a chance distribution. 



The random spacing of the suspended particle clouds was visibly 

 apparent when viewed along the sand ripple length. The clouds and voids 

 of suspended particles were most sharply defined directly above the 

 sand ripple crests and at the instant of wave crest passing. During 

 the instant of flow reversal, near and along the bottom, the major 

 portion of the suspended sediment load appears to be concentrated 

 directly above the sand ripple crests. In contrast for the same instant 

 of time there appears a scarcity of suspended particles directly above 

 the sand ripple trough. For the same wave conditions tested the analysis 

 and comparison of the data indicate the existence of much higher sedi- 

 ment concentrations directly above the sand ripple crest, as contrasted 

 to the very low concentrations found directly above the sand ripple 

 trough. As a consequence of this sharp sediment concentration gradient 

 from sand ripple crest to trough the selection of the sampling nozzle 

 position becomes important in laboratory measurements. Therefore, the 

 nozzle position for laboratory sampling measurements should be care- 

 fully selected and thus become part of the sampling data and analysis. 



The data on several samples for each of the three nozzle orientations 

 (illustrated in Figure 10 a,b, and c) are contained in Table 2. A com- 

 parison of the expected consistency of sampling results based on the 

 three sets of data was inconclusive. In the first place there was not 

 enough data and secondly the wide scatter of the data reduces any con- 

 clusion to doubtful speculation. Despite this however, it was interesting 

 to note the apparently higher values of sediment concentration and 

 somewhat better consistency of results obtained, by using a nozzle 

 oriented normal to wave crest and pointed seaward. 



At this point the question may be asked as to why the tests were 

 conducted using a nozzle orientation directed normal to the direction 

 of flow. The answer, as stated earlier in this report, is that the 

 horizontal orientation directed normal to the flow was reasoned to be 



56 



