(/) 



UJ 

 UJ 



-50 



-40 



-30 



-20 



-10 



+10 



NET ACCRETION/EROSION- 



1979 

 TROPICAL CYCLONE 



EROSION 1979 



1979 ACCRETION 



TROPICAL CYCLONE 

 EROSION 



9rK\''. FRONTAL EROSION 



BAY 

 MARCHAND 



BAY 

 CHAMPAGNE 



Figure 14. Shoreline erosion-accretion graph illustrating the contributions 

 of extratropical and tropical cyclones to coastal changes along the Caminada- 

 Moreau coast. Tropical cyclones accounted for over 70 percent of the erosion 

 experienced in 1979, Extratropical cyclones (frontal erosion) accounted for 

 approximately 30 percent of the annual erosion. 



Timbalier Islands . Timbalier Island and East Timbolier Island are the western 

 flanking barriers of the Bayou Lafourche headland. These barriers are composed of sand 

 that was transported west from the erosional headland source and that bypassed Belle 

 Pass (Figure 8). East Timbalier Island is a marginal recurved spit similar to the 

 Caminada Pass spit, and has repeatedly been detached from the erosional headland while 

 eroding at rates that exceed 15 m/yr. Flanking barrier islands are formed when a 

 marginal spit detaches from the headland. This occurrence is generally associated with 

 tropical cyclone landfall and barrier breaching. The updrift shoreline controls the 

 orientation of the newly detached island. Updrift erosion and downdrift accretion cause 

 rapid lateral migration and determine the stability of the island (Figure 13). Timbalier 

 Island, an example of a detached flanking barrier, eroded on the updrift end at an 



28 



