259. From the dimensional regression equation, Equation 14, the dimen- 

 sionless fall speed was identified as an important quantity. By normalizing 

 with wave period, the quantity thus obtained was related to the dimensionless 

 fall speed according to 



aT = 117 



Ho 



wT 



(15) 



260. The coefficient of determination was only 55 percent, but Case 700 

 contributed to more than half of the sum of the residuals. The reason is 

 probably due to a decrease in wave height that occurred between 20-30 hr 

 during the run, strongly affecting buildup of the bar. 



Bar location and speed of movement 



261. Movement of a bar during wave action is perhaps most accurately 

 characterized by its center of mass x^m • The bar crest, which is the most 

 convenient measure of bar location, especially in the field, is not as 

 accurate a measure since the shape of the bar changes during the course of its 

 growth, influencing the location of the crest more than the center of mass. 



In general, the mass center of the bar moved offshore on an erosional profile 

 unless a more shoreward bar grew together with the main breakpoint bar. 

 Actually, if a secondary bar merged with the main bar, further clear movement 

 of the bar conglomerate was absent. On an accretionary profile, the small bar 

 that formed moved somewhat onshore or was stationary. 



262. In Figure 22(a and b) , the horizontal location of the mass center 

 is shown as a function of time for the CE and CRIEPI experiments. Distance 

 was measured from the intersection of the initial profile and the still -water 

 level . Bars formed on a beach composed of coarser grains in general moved 

 less than those on beaches composed of finer grains under the same wave condi- 

 tions (compare Cases 400-401 and 500-501). Case 911, which involved a 

 sinusoidally varying water level, showed back -and -forth movement of the bar in 

 response to the change in water level , an effect not observed in control 



Case 901 (fixed water level). 



263. It was difficult to detect trends in the movement of the vertical 

 position of the bar center of mass. For bars formed on accretionary profiles, 



94 



