^ 2 



on 



o 

 o. 





CE 









Case 



300 







hr 







D 



01 





= Location of average 



U 



1-3 

 3-5 





still-water shoreline 



+ 



5-10 







X 



10-15 











15-20 







V 



20-30 







a 



30-40 







* 



40-50 







Distance from Initial Shoreline (m) 



Figure 50. Time behavior of net cross -shore sand transport rate 

 distribution on the foreshore 



angle after shearing) . Sediment transport produced by slope failure is 

 expected to occur very rapidly and would produce a transport rate distribution 

 of a quadratic shape since the step rotates at a fixed angle around some point 

 along its face. Averaging of the net transport rate smooths over the process 

 of avalanching. Also, the progress of avalanching is probably not ideal with 

 a pure and constant steepening of the step face; rather, transport is probably 

 greater at the base of the step, undermining it. 



Summary 



374. Calculated distributions of the net cross -shore transport rate 

 from profile change measured over intervals on the order of hours displayed 

 very regular and smooth properties despite the random character of the grain- 

 by-grain movement that actually took place. It therefore appears possible to 

 estimate the net cross -shore sand transport rate with sufficient reliability 



153 



