CONCLUSIOhJS 



1. Louisiana suffers from the most severe coastal barrier erosion and land loss problem 

 in the United States. 



2. Patterns of natural shoreline change and erosion problems associated with coastal 

 structures are interpreted using the model for deltaic barrier evolution presented 

 here. With increasing age, coarse-grained sediments of abandoned Mississippi River 

 deltas first form an erosional headland and flanking barriers, Stage I, then 

 transgressive barrier island arc, Stage 2, and finally a subaqueous inner shelf shoal, 

 Stage 3. 



3. Central erosional headlands and updrift ends of flanking barrier islands naturally 

 retreat rapidly, while downdrift, the ends of the flanking barriers accrete. The 

 sediment-dispersal system of an erosional headland and its flanking barriers is easily 

 disrupted by coastal structures. Placement of structures updrift from flanking 

 barriers causes severe erosion of the marginal spits and reduction of barrier island 

 area. Placement on the downdrift end of flanking barrier islands leads to island 

 accretion and downdrift erosion farther downdrift. 



4. Shoreline orientation to the dominant southerly wave approach determines patterns 

 of shoreline change in transgressive barrier island arcs. The Chandeleur Islands, 

 oriented to the north/south, have progressively decreasing rates of erosion 

 northward in the direction of predominant sediment transport. The Isles Dernieres 

 are oriented east/west and are characterized by frontal retreat and island 

 segmentation and deterioration. 



5. Tropical cyclones and extratropical cyclones are the dominant factors influencing 

 shoreline change in the central erosional headlands and transgressive barrier island 

 arcs. The placement of coastal structures predominantly influences patterns of 

 shoreline change in the flanking barrier systems. 



RECOMMENDATIONS 



1. Develop a comprehensive barrier island management plan that incorporates annual 

 beach nourishment in strategic locations, along with a vegetative 

 maintenance/research program. 



2. Avoid the band-aid approach to coastal zone management. Shoreline protection 

 plans that address site-specific problems typically fail because their scope is too 

 small, not taking into account the natural working of the whole coastal system. 



3. Restrict pipeline landfalls and transmission routes to environmentally sound 

 corridors that can be monitored and managed to reduce habitat damage. Backfill 

 and revegetate all existing pipeline right-of-ways in each barrier system to reduce 

 the breaching potential at these weak spots. 



4. Avoid using coastal structures such as groin systems and rip-rap seawalls; these 

 protection measures have proved ineffective at critical erosion areas in Louisiana. 



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