ABOUT THE BASIN
Splitting off from the Mississippi River near Simmesport, Louisiana, the Atchafalaya River, on its way to the Gulf of Mexico, is the flowing lifeline of the nation's largest river swamp - the Atchafalaya Basin. Atchafalaya is a Native American word, named in the Choctaw tongue: "hacha" for river and "falaia" for long.
Home to some of Louisiana's signature wildlife - alligators, roseate spoonbills, water moccasins and crawfish, to name a few - and spectacular views of the intersection of plant life, animal life, water and weather, the Atchafalaya Basin has long called to fishermen, photographers, hunters and those who simply want to experience nature.
As the river's flow has marked the generations, people have made different aspects of what is now the Atchafalaya Basin spillway part of their heritage. From the Native Americans who made their homes there to the loggers and fisherman who used the natural riches of the basin to make their livelihoods, the natural resources of the Atchafalaya Basin have shaped the modern culture of Acadiana.
The Atchafalaya Basin is the nation's largest river swamp and one of America's most productive ecological regions. However, like other water resources, this system faces many stresses and challenges, including several cited in a 2001 U.S. Geological Survey fact sheet, "The Atchafalaya Basin - River of Trees." These include:
Natural changes and human-induced modifications have resulted in the alteration of the ecology of this resource and will continue to do so.
Since 1932, there has been a net accretion of nearly 2.5 billion cubic meters of sediment in the Basin floodway, converting much open water and cypress swamps to bottomland forest.
Spoil banks, oil field canals and natural levees inhibit the historical sheeting pattern of water flow, causing hypoxic conditions (poor water quality) within nearly all of the large, interior swamps.
Invasive Exotic Plant Species
Massive growth of hydrilla, salvinia, giant salvinia, and water hyacinth restricts access to many areas in the Basin and exacerbates hypoxic conditions in the swamps.
Land Use/Resource Management
Diverse and sometimes conflicting activities within the Basin occur with regard to flood control, commercial fisheries, navigational, petrochemical, silviculture, recreational, environmental, and cultural interests.
Settling the Basin
The Atchafalaya River became a distributary of the Mississippi River about 1,500 years ago. Its drainage basin is naturally bounded by former Mississippi River paths, forming the Bayou Teche ridge to the west and the Bayou LaFourche ridge to the east. Native Americans have resided in the Atchafalaya Basin for at least 6,000 years, and the Acadians, who provided the basis of the modern Cajun culture, began to settle there in 1764. The Acadians built their homes on high ground along natural waterways and constructed levees to keep floodwaters out. After the Louisiana Purchase, large numbers of more affluent settlers from the Atlantic coast began moving to Louisiana and developing plantations (Reuss 2004). With the influence of these settlers, the importance of flood control and drainage for agriculture increased. Increased agricultural production meant that the importance of navigable waterways for commerce also increased. Bayou Teche, Bayou Plaquemine, and Bayou LaFourche were all important navigation routes within the Atchafalaya Basin.
Draining the Wetlands
As human population grew, pressure to change the natural attributes of the Atchafalaya Basin increased. Until very recently, wetlands were not recognized as having inherent value but were seen as wastelands not fit for human habitation and as areas that needed to be drained in order to be developed or put into agricultural production (Patrick 1994). This was the general attitude toward the Atchafalaya Basin throughout the 1800s and for most of the 1900s. Efforts to "improve" or "reclaim" the area were focused on centralizing and channelizing flow and removing obstacles to navigation such as beaver dams and log jams (Reuss 2004). All of these actions effectively reduced floodplain connectivity. Connectivity allows regular flooding and draining of forested wetlands and is essential for a healthy, functioning ecosystem. The Swamplands Act of 1849 furthered the goal of wetland drainage by allowing the United States to cede all of Louisiana's wetlands to the state, which the state then sold to private interests in order to raise money for reclamation projects, primarily levee-building and de-snagging projects. Additionally, the Timber and Stone Act of 1878 sold public lands "unfit for agriculture" to be used for lumber and mining activities. These actions resulted in the harvesting of all old growth forests in the Atchafalaya Basin, though some isolated patches of trees remain. Only in recent decades have scientists begun to understand and relay the important functions of wetlands for water quality, flood control, and carbon storage; in the Atchafalaya Basin, these developments in human thought came after major irreversible changes to the region's hydrology and ecology.
Re-routing the River
The first major human intervention changed the relationship between the Mississippi and Atchafalaya Rivers. In 1831, Henry Shreve built "Shreve's Cutoff" in the Mississippi River, which substantially decreased flow to the Atchafalaya by shifting the main channel of the Mississippi River eastward, away from the Atchafalaya. To counter increasingly diminished flow and improve navigability, the second major human intervention was initiated. Work to clear a series of massive log jams in the Atchafalaya River began in the 1830s and was completed in 1860. This action drastically increased flow to the Atchafalaya River (primariliy from the Red River), and channel depth below Old River increased from about 2 feet to more than 20 feet by the 1880s (Reuss 2004). The increased carrying capacity convinced many engineers that a large flood could allow the Atchafalaya River to capture the entirety of the Mississippi River's flow. Because the Atchafalaya River provides a shorter, steeper path to the Gulf of Mexico, it is the preferred route forwaters of the Mississippi River. In the absence of human intervention, the Mississippi River would have likely taken this route eventually.
Debating Flood Control
Noting decreased flooding after Shreve's cutoff was constructed, Atchafalaya Basin residents began to advocate for the complete separation of the Atchafalaya and Red Rivers from the Mississippi (Reuss 2004). The question of whether to close the Atchafalaya River to the Mississippi River or to keep it open as a floodway was debated by scientists, engineers, and politicians from the late 1800s until 1963 when the Old River Control Structure literally cemented the Atchafalaya River's future. Flood control along the Mississippi River was the primary directive for the Corps, so the needs of the Atchafalaya Basin were secondary considerations. However, closing the Atchafalaya River (and all distributaries of the lower Mississippi River) was supported by some as a means of forcing the Mississippi River to scour a deeper channel with greater carrying capacity. Others argued that the Mississippi River alone could not contain a large flood and that the Atchafalaya River should remain open to provide an emergency outlet for the inevitable floodwaters. Ultimately, the Atchafalaya River was left open to provide a floodway for the Mississippi River, but the general policy of closing outlets to increase river capacity was adopted. All of the natural outlets on the Mississippi River, with the exception of the Atchafalaya River, were eventually closed. Similarly, 22 of the Atchafalaya River's natural distributaries were later closed to accelerate development of the main channel (Reuss 2004).
Building the Floodway
Between 1850 and 1950, the combined flow of the Red and Mississippi Rivers entering the Atchafalaya River increased from less than 10 % to approximately 30 % (Reuss 2004). By 1954, the Corps had decided that a major intervention would be necessary to prevent the Atchafalaya River from capturing the flow of the Mississippi River. Additionally, the great flood of 1927 made it clear that levees alone could not protect life and property along the Mississippi River in the event of a major flood and that a "safety valve" would be necessary. These factors resulted in the Atchafalaya River being designated as a floodway, and the Old River Control Structure was completed in 1963 to maintain the flow to the Atchafalaya River at 30 % of the combined Red and Mississippi River flows. Soon after, the environmental movement gained momentum in the United States, and ecological considerations were mandated for large federal projects. The Corps completed its Environmental Impact Statement (EIS) for the Atchafalaya Basin Floodway System in 1982, which included a system of levees to contain the floodwaters to a designated area as well as measures to protect or improve environmental quality.
Considering the Environment
The Atchafalaya Basin Floodway System EIS assessed the environmental effects of the Corps' efforts to convert the Atchafalaya Basin into a floodway. Acknowledging that the primary negative environmental effect of the project was sedimentation, the Corp included two potential modifications for sediment control. These were 1) the realignment of the four principle distributaries of the Atchafalaya River to minimize sediment transport out of the main channel, and 2) construction of sediment traps at the heads of these distributaries to further reduce sediment transport. Citing the high cost of maintaining sediment traps as well as the environmental degradation that would be caused by spoil disposal into backswamps, the Corps selected only channel realignment as a sediment control measure. Additionally, the selected alternative included 13 water management units, which would be designed "to retain or restore unique environmental values." Two of these units, Buffalo Cove and Henderson Lake, were chosen as pilot projects. Another component of the selected alternative was the acquisition of real estate for recreational opportunities and public access.
Funding the Floodway
The Water Resources Development Act of 1985 and 1986 authorized funding for the Floodway System including channel realignments, water management units, and recreational features. It also laid out a cost share formula between the federal and state goverments in which the state was required to pay 25% of the operation and maintenance costs of projects associated with the water management units and 100 % of the operation and management costs associated with recreation projects. In 1996, Governor Mike Foster directed the Department of Natural Resources to be the lead agency in the development of a plan to meet the state's responsibility. The State Master Plan was completed in 1998, and the Atchafalaya Basin Program was created to carry out its goals.
Reuss, Martin. 2004. Designing the Bayous: The control of water in the Atchafalaya Basin 1800-1995. Texas A & M University Press. College Station, TX.
Patrick, W. H. 1994. From wastelands to wetlands. Journal of Environmental Quality, 23(5), 892-896.