bed agitation can be calculated using Figure 1 or equation (8) with a 

 given wave height and period. Factors ignored in the presented develop- 

 ment, such as tidal currents, sand size, and bottom slope, can clearly be 

 pertinent to the limit depth of the active beach, but wave height and 

 period have long been recognized as dominant factors in beach processes. 

 Crucial and somewhat arbitrary choices are taking $g = 1 and e = 0.03 

 in using equation (2) . Since the calculated limit depths for natural 

 beaches are about 30 feet, (edg/2) is about 0.5 foot and the wave energy 

 can raise bed sand above large, natural ripples with heights up to 0.5 

 foot (Inman, 1957). Thus, the criterion used for intense bed agitation 

 is internally consistent with calculated results. 



Calculated depths agree with measured water depths over the terrace 

 frequently cut into plane slope of fine sand by constant laboratory wave 

 action. For high waves expected 12 hours per year, calculated depths 

 agree with previously published conclusions on the yearly limit depth 

 to the active beach profile. With a more extreme wave condition as inputs 

 the calculation procedure could provide an estimate of the seaward limit 

 over a longer period; however, field data are not available to check such 

 an estimate. The present results encourage further evaluation of the 

 proposed calculation procedure. 



