survey maps for 1869-1956, together with a series of land cover maps at the scale of 

 1:10,000, based on 1979 aerial photography. Results are presented as a time series of 

 variation in coastal barrier area plotted against tropical cyclone and coastal structure 

 impacts. 



GEOLOGICAL FACTORS RESPONSIBLE FOR COASTAL BARRIER EROSION 



Deltaic evolution of the Louisiana coast is characterized by alternate periods of 

 land building and land loss (Figure 2). The alternation of these two activities is 

 determined by the balance between sediment supply and variation in relative sea level 

 (Curry 1964). Throughout the Pleistocene Epoch, the relative sea level has undergone 

 dramatic fluctuations, falling over 120 m and rising as much as several meters above 



Figure 2. A time series of paleographic maps depicting the evolution of the 

 Mississippi River deltaic plain and its depositional environments (modified 

 from Frazier 1967) . 



16 



