are composed of well-rounded, well-sorted, fine-grained sand. 



4. Because Isles Dernieres are so important to the residents of Terre- 

 bonne Parish as a protective front, their rapid decrease in size has become a 

 major concern in recent years. Increased erosion, due to this size-decrease, 

 is responsible for the destruction of commercial and residential property on 

 the mainland as well as the loss of coastal wetlands. The land loss on Isles 

 Dernieres has been well documented by Peyronnin (1962) and Meyer-Arendt and 

 Wicker (1982), but the dispersal of the eroded material has not been studied 

 in detail, especially as it relates to migration. This investigation analyzes 

 trends in the factors controlling migration from 1887 until 1980 and any 

 changes that may have occurred within those trends. 



5. The migration of Isles Dernieres is controlled mainly by overwash, 

 longshore drift, tidal inlet formation, and subsidence. Wind action plays a 

 very minor role and therefore was not evaluated. The purpose of this study is 

 to define the migration of Isles Dernieres since 1887 by quantitatively evalu- 

 ating the various processes controlling migration and to document how these 

 processes have changed through time. To accomplish this, recent and historic 

 topographic maps and hydrographic charts were used to place quantitative 

 values on the erosion and deposition related to each factor affecting the mi- 

 gration of Isles Dernieres. These values can be used to explain the evolution 

 of the island group, speculate about its early history, and make some predic- 

 tions about its future. 



