GO 



to 

 CD 

 Q. 



_o 



CO 



GO 



TO 

 CO 



CE.CRIEPI 



Average More-Seaward 



More-Shoreward 



Elapsed Time (hr) 



Figure 26. Evolution of seaward slopes of main breakpoint bars 



278. Since average shoreward and seaward bar face slopes were consid- 

 erably different, the bars were asymmetric in shape. The average shoreward 

 bar slope was always steeper than the corresponding average seaward slope, 

 making the bar positively skewed. 



279. Bar face slopes encountered in the field are, in general, milder 

 than slopes in the CE, CRIEPI, and other tank studies involving regular waves 

 and constant water levels. Under laboratory situations, the smoothing effect 

 on the profile of random waves and varying water level which normally exist in 

 nature (e.g., Keulegan 1948) is absent. For example. Hands (1976) found that 

 maximum bottom slope was less than 10 deg for numerous measurements of Lake 

 Michigan bars (varying waves but constant water level). On the basis of 

 frequent and repetitive high-accuracy surveys on an Atlantic Ocean beach over 

 5 years, Birkemeier* found that steepest shoreward bar slopes of approximately 



Personal Communication, 1987, William Birkemeier , Hydraulic Engineer, 

 Coastal Engineering Research Center, Vicksburg, MS. 



104 



