Qrt 



Q/t 



mi, iiiif^mm^^^m^ 



Overlapping Offset 



Qrt 



Adequate 

 updrift source 



Q/t 



Length of orrows indicotes 

 relative magnitude of 

 Longshore Transport Rate 



Updrift Offset 



Inadequate 

 updrift source 



Downdrift Offset 



Qrt Qit 



Negligible Offset 



(Galvin,l97l ) 



Figure 4-57. Four types of barrier island offset. 



4- 141 



