illustrates the slow recovery of the bar shown in Figure 4. Recovery did not 

 begin until the following February and continued for the next 6 months, an 

 extended period of low wave height conditions. Recovery of shallower bars 

 can be rapid. Sallenger, Holman, and Birkemeier (1985) measured a rate of 

 onshore bar migration within the surf zone of 1.2 m/hr during the waning 

 stages of a storm when the waves were 2 m high with a 14-sec period. 



23. Given a sufficiently long period (several months or more) of low 

 waves, the storm bar may disappear (e.g., Birkemeier 1985a). If, however, 

 the storm bar is located in very deep water, the bar may not be erased over 

 an extended time scale of many years. In this case, if no other source of 

 sand is available, the beach suffers from an apparent permanent erosion (Dean 

 1976). 



Overwash 



24. "Overwash" is a process which occurs when the storm surge and wave 

 uprush overtop the foredune line causing water and sand to move inland. 

 Overwash is of major importance during extreme storms when a significant 

 percentage of a duneline may be overtopped or breached (Figure 6). It is an 



Figure 6. Breached and overtopped dune on Grand Isle, Louisiana, 

 following Hurricane Juan in 1985 



13 



