13 



The factors controlling the position of the bar at the time it becomes 

 relatively stable are stated in equation 4. The results of the tests to 

 evaluate the terms in equation 4 are plotted on figure 7. Figure 7A 

 shows the relation between ao/Hs i. e., the ratio of wave height to the 

 depth of bar base; and the wave steepness, agXo. 



It appears that for the same value of wave steepness, flo/Xo, the 

 initial slope i, of the beaches did not affect the ratio aolHa. If an 

 effect is present, it is of the order of the error of observation. 



Since the points are plotted without differentiating between the 



- values of the ratio -^^ and do not scatter to any great extent, it may 



be concluded that the effect of this ratio, if present, also cannot be 

 larger than the observation error. For example, considering the 

 following pair of data taken from the records: 



Xo=48 ft., a^/Xo=0.06, ao/He^ 0.50 



Xo=18 ft., a<,/Xo=0.06, a<,/i!ZB=0.45 



a 300 percent variation is indicated in the -j^ values, yet the variation 



in the values of the ratio aJHs is only 10 percent. 



Interpretation of the curve in figure 7A leads to the conclusion that 

 if the water depth remains constant, the depth of bar base and con- 

 sequently, the position of the bar, formed by a single system of waves 

 is a function of the wave height, ag, and wave steepness a<,/X<,. If the 

 water depth and wave steepness are held constant, an increase in the 

 wave height will move the bar seaward. Furthermore, if the water 

 depth and wave height are held constant, an increase in the wave 

 steepness will move the bar shoreward. Further, if the wave height 

 and wave length are held constant, Hg, wiU likewise remain constant, 

 and any increase in the depth of water moves the bar shoreward. 



In figure 7B the data from the beaches of different slopes are plotted 

 individually. No distinction is made, however, between the tests 

 made in the large and small tank. Similarly, no differentiation is 

 made between points associated with the variable sand parameter, 

 XoMcM- It should be noted that the ratio of the depth of bar crest 

 to the depth of bar base HJHb, is practically independent of the wave 

 steepness ratio ^o/Xo, and of the slope i. Since the data covers a wide 

 variation in the values of the ratio XoMgm, it may also be inferred that 

 the ratio HJHb is likewise independent of the ratio \o/doM within the 

 order of the error of the observations. The data as plotted in figure 

 7B give a constant value 



Hc/Hb=0.58 (12) 



