sediment in an average year (U.S. 

 Army Corps of Engineers 1970). Most 

 of the present estuarine-marsh com- 

 plex owes its existence to the delta- 

 building process of the Mississippi 

 River. Historically, the Mississippi 

 River annually overflowed the vast 

 marshlands and estuaries, depositing 

 sediments throughout the flood plain 

 and also in the shallow waters of the 

 Gulf of Mexico, over the continental 

 shelf. The sedimentation from these 

 yearly floods generally exceeded in 

 total effect the attritional pro- 

 cesses of erosion, compaction, and 

 subsidence, so that the shoreline ad- 

 vanced seaward (U.S. Army Corps of 

 Engineers 1970) . 



Investigations have disclosed 

 that continuing change is taking 

 place in nearly all of the important 

 physical and chemical parameters 

 from which the area derives its 

 unique character. Further, it has 

 become apparent that these changes 

 relate, in the long-term sense, pri- 

 marily to the alteration of the over- 

 flow regimen of the Mississippi Riv- 

 er. In the past 250 years, man has 

 increasingly restricted the river 

 overflow into the estuarine zone in 

 Louisiana through the construction of 

 works to control devastating floods 

 and to provide for dependable naviga- 

 tion. Deprived of the overflow, with 

 its nourishing sediments, the area is 

 yielding to the sea through subsi- 

 dence and erosion. Another important 

 source of change in Louisiana's estu- 

 arine area is the development of the 

 area for various economic pursuits, 

 particularly those associated with 

 the fisheries and petroleum indus- 

 tries. The construction of new wa- 

 terways to service these industries 

 has had a profound effect on salini- 

 ties and flow patterns in the area 

 (U.S. Army Corps of Engineers 1970). 



ESTUARINE AREA STUDIES 



A number of agencies at the 

 Federal, State, and local level have 

 recognized the changing conditions of 

 the Louisiana estuarine environment. 

 As a result, Congress has directed 

 the U.S. Army Corps of Engineers to 

 undertake certain investigations to 

 determine the feasibility of provid- 

 ing water resource improvements in 

 the interest of conservation and en- 

 hancement of fish and wildlife re- 

 sources. The U.S. Army Engineer Dis- 

 trict, New Orleans, has conducted 

 several investigations involving di- 

 version of freshwater from the Mis- 

 sissippi River to portions of the 

 estuarine area. The earliest study, 

 conducted in the late 1950' s, re- 

 sulted in the congressional authori- 

 zation of the Mississippi Delta Re- 

 gion Salinity Control project. The 

 project, which is depicted in Figure 

 1, was authorized by the Flood Con- 

 trol Act of 1965 as part of the Com- 

 prehensive Plan for Modification of 

 Flood Control and Improvement of the 

 Lower Mississippi River (U.S. Army 

 Corps of Engineers 1979). It con- 

 sists of four gated-water or salin- 

 ity-control structures on the banks 

 of the Mississippi River with con- 

 necting levees and channels that will 

 introduce fresh water from the Mis- 

 sissippi River to the bays and 

 marshes of the Mississippi Delta. 

 Salinity-control structures would be 

 located on the east bank of the river 

 at Bohemia and Scarsdale and on the 

 west bank at Myrtle Grove and Home- 

 place. The objective of the project 

 is to increase wetlands productivity 

 by the establishment of an ecological 

 regimen favorable to the production 

 of oysters, shrimp, fish, furbearing 

 animals, and migratory waterfowl. The 

 current estimated cost of the project 

 is $30,000,000, of which $22,500,000 



367 



