between Vermilion Bay on the west and the Chandeleur Islands on the east (Figure 2). Most of 

 this very extensive deltaic plain complex is presently known as the Louisiana Wetlands. 



DESCRIPTION OF THE DELTAIC PLAIN COMPLEX 1 



Each of the four large deltas (Teche, St. Bernard, Lafourche, and present delta shown on Figure 

 2) is characterized by distinct landforms, or components, which have their own unique character 

 (Figure 2-A). 



Bayous and Natural Levees 



The highest land in southeast Louisiana is about 25 ft above sea level and occurs along the 

 major bayous, which are remnants of much larger channels of the Mississippi River. Through the 

 years river waters and sediments spilled over the banks of these channels to create natural levees 

 which consist of well-drained soils. 



Swamps 



The second major component of the deltaic plains is the swamps which occur at lower elevations 

 between the bayous and natural levees. The swamps cover an area of about 2,000 mi 2 and include 

 a large variety of trees and wildlife. 



Freshwater Marshes 



Seaward of the swamps the land is covered with freshwater marshes which lie only a few feet 

 above sea level. These marshes are occasionally covered with brackish water; hence they are 

 devoid of trees. There are over 1,600 mi 2 of freshwater marshes in southeast Louisiana. 



Brackish and Saltwater Marshes 



The coastal part of the deltaic plain complex consists of brackish and saltwater marshes which 

 comprise the most significant portion of the wetlands. These marshes cover an area of 

 about 4,300 mi 2 and they rise only a few inches above sea level. They include hundreds of small 

 lakes, ponds, and small bayous. 



Inland Lakes 



Southeast Louisiana is well known for its beautiful lakes. Nine of the largest lakes, which are 

 indicated on Figure 2 (by capital letters A through I), all originated in the same manner. About 

 30,000 years ago ice accumulated on North America as far south as southern Illinois and the level 

 of the sea in the Gulf of Mexico dropped about 450 ft. Over 100 mi of the Continental Shelf off 

 south Louisiana was exposed "under the sky" (Figure 3). About 15,000 years ago, as the ice began 

 to melt, sea level began to rise. About 4,000 years ago sea level reached its present stand and 

 most of southeast Louisiana was transgressed by the Gulf of Mexico to as far north as the latitude 

 of Baton Rouge. When the Teche Delta was formed, it isolated what is now Grand Lake and 

 Lake Verret from the gulf (Figure 2). The subsequent development of the St. Bernard Delta to 

 the east isolated Lake Maurepas and Lake Pontchartrain from the gulf. Four other lakes (Lac des 



1 Reader should refer to the Geological Map of Louisiana published by the Louisiana Geological 

 Survey, Baton Rouge. 



