Managing the Lower Mississippi River Landscape for Strategic Navigational and Flood Control

The Lower Mississippi River flows from the confluence of the Ohio River and Mississippi River at Cairo, Illinois into the Gulf of Mexico. Mississippi River and Ohio River pathway shifts have shaped and re-shaped the landscapes through which they flow and where their sediment-laden tributary waters co-mingle at the confluence on the voyage to the Gulf of Mexico. For much of their history, the lands adjacent to the Lower Mississippi River were bottomlands that flooded with the seasons unconstrained by human river training structures. Since 1717 European nations have fought over strategic navigational control of the Mississippi River. After the Louisiana Purchase in 1803, the United States took controlled the Lower Mississippi River. During the Civil War, from 1861-1865, the Union and Confederate forces battled for navigational control of the Lower Mississippi River. The primary objective of this paper was to highlight how the strategic navigational and flooding control of the Lower Mississippi River and geological and landscape resources were responsible for the successful economic development of this rich historical region of North America.


Geological History of Mississippi River Valley South of Cairo
The rapid abandonment of old river channels and the creation of new channels are evident throughout the Lower Mississippi River valley ( Figure 4). Fluctuations in glacial meltwater and sediment deposition during warming intervals affected river channel slopes led to these avulsions. Channel slopes are reduced and become unstable when the river carried more sediment than the water could Open Journal of Soil Science  With an increase in sediment deposits, the river bed becomes higher than the floodplain; and became easier for the river to breach its natural levees.
Breaching, which occurred during flood events, caused the river to spill out of its old channel and create newer ones as the water sought more stable slopes and shorter routes downstream.
Historically the Mississippi River has entered the Lower Mississippi River valley through three channel paths: 1) an opening cut between the Ozark Plateau and the northern end of Crowley's Ridge [8]; 2) the 16  souri and now at Cairo, Illinois [8]. Historically, this region has been a delta, confluence and bottomlands dating back 30,000 to 800,000 years BCE.

Mississippi and Ohio River Landscapes
The Mississippi and Ohio rivers converge at the northern edge of an ancient sea and lowlands of the Mississippi Embayment. A land bridge separates the Central Interior Lowlands from the Gulf Coastal Plain ( Figure 6). This upland land bridge, the Shawnee and Ozark Hills, connects the Southern Appalachians and the Ozark Highlands [8]. Plants and animals used this land bridge ( Figure 6) to migrate between the Southern Appalachians and the Ozark Highlands. The ancient Ohio and Mississippi rivers are overlain on the land bridge to help the reader   visualize its location [11]. The Ozark Highlands including the Francois Mountains ( Figure 7) were created by volcanic and intrusive activity approximately 1.5 billion years ago [12]. By comparison, the Appalachian Mountains began forming about 460 million years ago [11].  The ancient rivers, gulf coastal inland sea, and land bridge map of the Central Interior Lowlands affected the pathways and confluences the current great rivers and their tributaries. Melting glaciers as a result of a changing climate and seismic activity re-aligned the Ohio and Mississippi rivers over time. With the settling of the Midwest, the locations of these great rivers were often used as state boundaries and the size and shape of many states were affected by the geological events which formed and reformed these rivers [4] [13].

Strategic Navigational Control of the Mississippi River
The first attempt to control the Mississippi and tributary landscapes occurred in 1717. New Orleans, a deep water port, was established by the French on the Mississippi River 80 km up river from the Gulf of Mexico. The original city settlement site had an area of 14 city blocks with drainage ditches around each block and was the first strategic attempt to control the landscape. In 1718 the first levee may have been erected on banks of the Mississippi River but was never confirmed. The French documented levees were built in 1722. These levees were 1.2 m high earthen mounds began a 300-year history of combating high water with embankments in an attempt to control flooding [4]. The levees were sustained by private landowners, who used state slaves, prisoners, and poverty stricken Irish immigrants to perform the dangerous work. New Orleans had poorly-drained soils, unfavorable topography, and was only a few feet above the sea. The deltaic floodplain of the Mississippi River had a settling at a rate of between 0.6 to 3 m per century. Settlement on the Mississippi River Delta was prone to periodic flooding by the river.

Early European Settlement
More than two million people call the Mississippi River Delta their home ( Figure 8). The Delta location at the mouth of the Mississippi River allowed the

Bayou Teche
The Bayou Teche begins in Port Barre and flows southward to the Lower Atchafalaya River ( Figure 9) and was the primary means of transportation during the

Free State of Illinois in the Union
Illinois became a free state in the Union in 1818. Nearby states and neighboring

American Civil War
The American Civil War started in 1861. At that time Cairo, Illinois had a population of 2200 with only 55 African-Americans. The Port of Cairo ( Figure 14) became a strategically important training center and supply base for the Union army [19].        soils were extremely muddy, and prone to flooding despite some levees. The land was swampy, climate was humid, and disease-carrying mosquitoes and rats were everywhere [19].

The Impact of Union Gunboats on the Mississippi, Ohio, Cumberland and Tennessee River Waterways on the Outcome of the Civil War
The Union gunboats built at Mound City, Illinois ( Figure 16 and Figure 17) impacted operations on the river. These gunboats could transport thousands of Union soldiers to advance rapidly on the Lower Mississippi, Cumberland, Ohio and Tennessee rivers and often out-maneuver the Confederate Army and Navy. However, the Union forces also sustained losses and many of the troops killed in action were buried at the national civil war cemetery in Mound City ( Figure 18). Open Journal of Soil Science

Flood Control and the 1927 Flood
In   [23] and home to more than 931,000 people were inundated. Millions of hectares across seven states were flooded ( Figure 11). Evacuees totaled 500,000 and economic losses were estimated at US$1 billion in 1927 dollars which was equivalent to one-third of the federal budget. Post-1927, it was clear the Mississippi River levee system as designed was inadequate to protect against record high river levels.

Attempts to Reduce Ohio and Mississippi River Peak Flows after Flood of 1927
After  Recent levee breaching has created new knowledge about hydrology, soils, and the vegetation of rivers and their bottomland as a result of unexpected shocks to the river ecosystem. Despite the presence of well-engineered structures their occasional failure reminds us that the river landscape is a complex human-natural system. This complex system is ever changing, dynamic and often managed based on assumptions of steady state expectations where the past predicted the future. These assumptions do not prepare communities well to deal with often competing diverse societal goals under an increasing populations, increasingly variable climate, and intensified land uses [23] [24].
The Great Flood of 2011 [25] [26] and drought of 2012 [10] well illustrate some of the unintended consequences and vulnerabilities that arise from designing and managing river systems without taking into account their changing nature and the need for more flexible-adaptive capacities [23] [24] [27] [28]. Following the Great Flood of 1927 [20], it became apparent that the extensive use of levees (Figure 24), confinement and channelization of the rivers was inadequate to effectively contain the Mississippi River and tributaries [22]. The subsequent addition of reservoirs, including the Barkley and Kentucky, upstream of the confluence of the Ohio and Mississippi rivers and four downstream floodways ( Figure 24) below were a substantive shift by the USACE to strategically incorporate confinement engineering with a dispersion risk management strategy [21] [22]. The underlying premise of dispersion is to duplicate the natural floodplain functions of bottomlands which historically served as outlets to rivers under flood conditions.
The 2011 the Birds Point-New Madrid floodway induced levee breaching reaffirmed the effectiveness of dispersion management and its capacity to protect the integrity of communities and land uses along the larger river system. However, 74 years had lapsed since 1937, the first time the floodway was used. The new damage to 200 buildings including 75 homes (Figure 25), the loss of 12,000 ha of spring wheat and damage to over 400 cropland fields, the landowners and residents were unprepared for the consequences of opening the floodway. Reemergence of competing social values and social tensions has risen to reassess the uses of river bottomlands by public policy makers, environmental advocates, community leaders, and government agencies. They are challenged to defend the impacts and benefits of leveed structures that in recent history have protected rural agricultural and urban land uses. Although most river flooding has repetitive patterns reoccurring seasonally and over a period of years presenting known risks, floods are complicated in their range of duration and intensity and can result in unexpected consequences [29]. Structural failures including levee breaching ( Figure 26) are often the result of unusually high peak runoff in a system cut off from its historical floodplain. Science is just beginning to understand the relationship between the river and its floodplain, the roles of wetlands and riparian corridors and the beneficial aspects of flooding and as well as the extensive economic and social damaging floods wreak on the livelihoods of people working and living along the river.
There is evidence that a new type of river management is required, one that goes beyond the current confinement-dispersion strategy. Park et al. [24] call for resilience management, an adaptive management approach to changing conditions that preserves the natural functions of the river ecosystem in ways that minimize catastrophic failure of engineered structures. This concept is just emerging with many practical details remaining to be addressed. Some of these details involve the soil resource immediately after levee breaches and subsequent flood events [30] and better inventories and assessments. Updated land scouring and deposition surveys and soil surveys (Figures 27-29) can be used to guide restoration decisions when engaging and informing the public so as to come to politically acceptable agreement on management and land use decisions and create a better understanding of the ecosystem services the floodplain provides.

New Madrid Floodway
The key location of the flood control system on Lower Mississippi River is the

Flood Control Act of 1938 and 1944
One     When flood stage peaks on the Mississippi River or its tributaries subside, floodwater within the backwater already drains through pumps and floodgates. The Yazoo backwater area has no pumps.
There are four major backwater areas on the Lower Mississippi River ( Figure   24). These backwater areas are the result of Mississippi River levee system gaps left at the mouth of tributaries that empty into river [22]. Prior to the construction of levee systems these backwater areas flooded naturally during Mississippi River flooding events. The levee system actually protected the backwater areas from flooding but during flooding events water backed up through the gaps at the lower end of the levee and inundated the low-lying areas behind the levees.
The 1928 levee project did not attempt to protect these major backwater areas

Impact of Encroachments in the New Madrid and West Atchafalaya Floodways
The           way has yet to be used therefore the disaster consequences to residences ( Figure  42 and Figure 43) living in the West Atchafalaya floodway are unclear and require study. Using aerial imagery and historical maps Lopez-Llompart and Kondolf [32] systematically measured the type, number, and spatial distribution of encroachments in the two floodways after the late 1960s. Encroachment in the Birds Point-New Madrid floodway decreased by one-half, while the number of encroachments in the West Atchafalaya floodway tripled, mainly concentrated along highways and adjacent to the levees. These encroachments created linear bands of higher hydraulic resistance [32]. The presence of encroachments clearly discourages operation of the floodways for their designed purpose. There are no known studies that have determined whether the presence of these structures would adversely and measurably affect flood hydraulic thorough the floodways.

Impact on People Residing in Floodways
The science of understanding the impacts of management of flooding is more than the calculations of flow rates, number of structures and levee lengths. The social, economic and political science on the impacts of well-planned and implemented policies on economic use, property and life protected versus the consequence of poorly implemented policies also needs study. The consequence of choosing to live in the Birds Point-New Madrid floodway in 1937 resulted in at least three direct known deaths, two flood related deaths and 30 post flood repairmen deaths, an unknown number of homes lost, 4000 acres of farmland destroyed by sand dunes, erosion and gullies and 12,000 displaced persons living in Red Cross Camps and given relief of $18 per month until they had income from their next crop harvest. In 2011 there was not any deaths, but few residents have returned and rebuilt [33].
The flood of 1937 apparently caused the Sharecroppers Demonstration of 1939 ( Figure 48). Some credence can be given to this claim since the two highways, where 1500 evicted tenant farmers and their families camped for four January, 1939 nights, are in or just outside of the floodway. However, farm policies of the Agriculture Adjustment Act (AAA), in the early thirties purposed to eliminate suffering with direct payments to farm tenants, are also implicated. These farm AAA programs, implemented during depression era of low commodity prices and low wages, enabled landowners to employ day labors utilizing new mechanization practices were able to claim the federal payments when tenant contracts were not renewed. On January 1, 1939 thousands of tenants in Southeast Missouri were evicted. Over the course of four years the roadside demonstrators were moved to nine local encampments and later, by 1943, settled in four federal sponsored communities.
The town of Pinhook, an African American community located in the Birds

River Training Program
The USACE has developed a river training program which has resulted in more   when the rivers were not above flood stage. The use of weirs to maintain the channel location on river bends are thought to keep sediment in suspension rather than being deposited in the river channel and requiring dredging.

Summary
Since 1717 strategic navigational control of the mouth of the Lower Mississippi River has been the goal of at least three European nations and the United States.
Initially France won. However, their claims were continually challenged by Spain.      ( Figure 24), floodways, aqueducts and an extensive system of reservoirs have been created to manage these rivers for navigation and to protect agriculture, communities, and other high value land uses. Navigation on the Lower Mississippi River does not require locks and dams. The West Atchafalaya floodway is the last feature of the Old River flood control complex to be used under the project design flow, the West Atchafalaya was not overtopped, breached, needed or used during the record Flood of 2011.

Conclusions
The location of the mouth of the Mississippi River allowed the Delta area to become the Gateway to the United States.  The combination of reservoirs, water storage areas and floodways were able to handle the major flooding events without the use of the New Madrid floodway until the Flood of 2011. Future major floods will happen. Maintenance of the existing system will be important to ensure the impact of these floods can be handled. Past lessons indicate floodway encroachment, which is now occurring in the West Atchafalaya floodway, can be consequential and significant outreach is still needed to mitigate future property damage and potential loss of life. The strategic navigational and flood control of the Lower Mississippi River and geological and landscape resources were responsible for the successful economic development of the Lower Mississippi River region of North America.