Environmental Science: Regional Updates

Managing Midwest Rivers
by Dr. Steve R. Overman

Introduction
Ole Man River just keeps rolling along. Among the most prominent environmental features of the Midwest is the Mississippi River and its vast network of tributaries. The Mississippi River system drains the Heartland of America from the Appalachian to the Rocky Mountains. For much of the Midwest, both the past and present are inextricably tied to these rivers. Early European explorers and later Lewis and Clark used these waterways as paths into the uncharted American wilderness. The great westward migration of the 19th century was facilitated by the extensive use of river transport. Today, the major rivers of the region are superhighways for barge traffic bearing the bounty of the Midwest's agricultural and industrial wealth. Population centers from large cities to small towns line the banks of rivers of the Mississippi River system.

Midwestern rivers have been and remain an invaluable resource to the region. Humans have manipulated and managed these rivers to improve their utility and value as a resource. The rivers have not always been benefactors, but at times have become terrible foes to human activities. Rampaging floods periodically strike rivers throughout the Midwest. The threat of floods has resulted in additional manipulation and management of Midwestern rivers.

History
Efforts to manage the Mississippi River System date back to at least 1718 when the first levees were built around the city of New Orleans. In 1824 Congress authorized the Army Board of Engineers at West Point to undertake waterway improvements along the Mississippi and its tributaries. This led to removal of snags and log jams to improve navigation of the river. Also, for the first time the Federal government joined early settlers of the region in construction of levees. Severe flooding in the Mississippi River System during the 1850's prompted Congress to authorize surveys and studies of the flooding problem. In 1861 two West Point engineers, Andrew Humphreys and Henry Abbott, presented their landmark study, Physics and Hydraulics of the Mississippi River. This study stated that levees were the only feasible approach to flooding in the Mississippi River Basin. This study was the philosophical bedrock of the Army Corps of Engineer's approach to management of the Mississippi River System for more than six decades. In 1879 Congress created the Mississippi River Commission to plan and coordinate engineering efforts to facilitate navigation and prevent destructive floods. The great flood of 1927 showed the inadequacy of the levees only approach to management of the Mississippi River System. The Jadwin Plan adopted by Congress in 1928 authorized construction of floodways to divert peak flows and hold down river levels in the main channel during times of floods. In 1968 Congress instituted the National Flood Insurance Program as a means of encouraging communities to examine land-use planning in floodplain areas. Huge and prolonged floods along the upper Mississippi and lower Missouri Rivers in 1993 stimulated extensive re-examination of efforts to manage the Mississippi River System.

Current Status
The Mississippi River Commission and the Army Corps of Engineers remain the key players in management of the Midwest's river resources. After the floods of 1993, cooperative relationships were established between these organizations and other Federal agencies including the Federal Emergency Management Agency, the National Oceanographic and Atmospheric Administration, and the U.S. Fish and Wildlife Service. Additionally, states affected by flooding during and since 1993 have become increasingly active in efforts to minimize impacts of future flooding.

Pro/Con Arguments
Like almost all complex environmental issues, there are pro and con arguments to this issue. There are both positive and negative human and environmental consequences to attempts to manage the Midwest's rivers.

Pro Arguments

1. Maintenance of a Navigation Channel

Major rivers of the Mississippi River System are vital routes for barge traffic. To maintain and improve navigation, the Army Corps of Engineers has straightened, shortened, and deepened parts of the river via dredging and construction of locks and dams. Sandbars, snags, and navigation hazards are regularly removed and the Corps has an extensive network of navigation buoys on the rivers. Use of the rivers as routes for barge traffic is essential to the commerce and economy of the Midwest.

2. Flood Protection

People, property, businesses, industry, and agricultural crops are at risk from the inevitable floods along the rivers. The Army Corps of Engineers has developed a monumental network of levees, dikes, berms, and floodwalls along the banks of the rivers intended to protect humans and human structures and enterprises from the threats of floods. These flood protection measures have been highly successful in the smaller, more frequent floods, but may actually exacerbate the very large, less frequent floods (see below).

3. Enhanced Utilization of Floodplains

The extensive levee system, along more than 3,000 miles of Midwest rivers, has allowed greater human utilization of floodplain lands adjacent to the rivers. This land has been developed for agricultural, industrial, commercial, and residential purposes. Without the levee system many of these areas, often wetlands, would have been less suitable for human development. Also without the levee system, these areas would have been subject to frequent flooding. This third benefit also has negative consequences as described below.

Con Arguments

1. Exacerbation of Major Floods

While the levee system has been effective in containing small floods, the levees may actually increase the severity of major floods. Levees prevent the rivers from spreading out over their natural floodplains. If a river spreads out over a large floodplain area, then the height of the water rise during a flood is relatively small. However, if a river is not allowed to spread out over a floodplain, then the water will rise much higher in the artificially narrowed river channel. Higher water levels may top existing levees resulting in flooding and calls for ever higher levees.

2. Human Developments in Natural Floodplains

Human habitation and development in flood-prone areas are invitations to disaster. The levee and floodwall system along Midwest rivers has encouraged development in floodplains and often provided a false sense of security. When floods do top or break levees in developed areas, the resultant damage is severe and costly.

3. Loss of Wetland and Riparian Ecosystems

Until fairly recently, wetlands were regarded as useless lands. Most of the former wetland areas of the Mississippi River System have been drained, developed, and protected by levees. Wetlands are now recognized as biologically-rich areas worthy of preservation. Riparian ecosystems are those natural areas immediately adjacent to rivers. Like wetlands, riparian zones are ecologically valuable. With human development and levee construction much of the riparian areas along Midwest rivers have been lost or altered.

4. Reduced Alluvial Soil Deposition

The fertility of floodplain soils is due in large part to deposition of new soils by periodic floods. Since the levee system prevents rivers from spreading out over floodplains and depositing their sediment load, deposition of fertile new soil is blocked.

5. Enhanced Soil Erosion and Sediment Load

Natural riparian zones help to trap soil eroding from lands adjacent to rivers. Loss of natural riparian zones results in more soil entering riverways by erosion. The amount of sediment a river carries is proportional to water velocity in the river. Because major rivers of the Midwest have been straightened, deepened, and artificially confined to narrow channels, water velocity and hence sediment load have increased. More and more precious topsoil from Midwest farms is being carried out into the Gulf of Mexico.

6. Adverse Impacts on Aquatic Life

Dredging of major rivers of the Midwest is commonplace to maintain the rivers as navigation channels. Dredging severely impacts benthic, or bottom-dwelling, species. Species found in the water column are adversely affected by the increased turbidity resulting from greater sediment loads found in the rivers. Loss of riparian and wetland areas, and chemical and nutrient pollution have also adversely impacted biota of Midwest rivers. The overall effect of these human-related changes has been to decrease the biological richness of aquatic ecosystems in the Mississippi River System.

Regulations
Floods of the 1990's have fostered new approaches to management of the Mississippi River System. The Hazard Mitigation and Relocation Assistance Act of 1993 makes moneys available to relocate home, businesses, and even entire communities out of flood-prone areas. Federal and state buy-out programs have been established to purchase agricultural lands damaged by flooding in order to allow these areas to revert to natural floodplains. These re-established floodplains will serve a dual function. First, they will provide "safety valves" by allowing the rivers to expand in breadth during floods, reducing the height to which flood water will rise. Second, these reclaimed floodplains will serve as wildlife habitats helping to partially restore the riparian and wetland ecosystems lost to past developments and levees.

Connection to Environmental Science

The effect of river channelization on downstream flooding is discussed on pages 288 - 289. Pages 304 - 306 describe the adverse impacts of excess sediment load on aquatic ecosystems. The ecological values of wetlands are discussed on pages 306 - 308. The need for dredging of riverways versus the impacts of dredging are considered on pages 311 - 312. Page 314 describes the role of riparian zones in reducing soil erosion into rivers.

Hyperlinks

Exploring the West from Monticello: This is an exhibition of maps and navigation instruments used by early American explorers.
If You Build It, It Will Come: This critical review of the effectiveness of some of the world's flood control systems, including that of the Mississippi River, was written as an honors program project by four students at the University of California - Davis.
Lewis and Clark Expedition: This is a comprehensive list of web sites related to the Lewis and Clark expedition.
Midwest Basic Resource Information: This useful site is provided by the US Department of Agriculture. The page provides information and links on Midwest resources.
River Alliance of Wisconsin: This is a conservation organization focusing on the issues related to the restoration and protection of Wisconsin rivers. American Rivers and Rivers Unlimited are other organizations that also sponsor legislation and support the protection of North American rivers.
SAST Database: The Scientific Assessment and Strategy Team was established after the 1993 flooding. This interagency unit has amassed a tremendous amount of environmental information for the upper Mississippi and lower Missouri River basins.
Stream Channelization: This site provides bibliographic citations for the biotic and abiotic effects of stream channelization.
US Army Corps of Engineers -- Mississippi Valley Division: This is the information web site for the main agency responsible for managing the Mississippi River System. The pages are interesting and informative and several are well illustrated.

References

Bayley, P. ÒUnderstanding Large River Floodplain Ecosystems.Ó BioScience 45:163-168, 1995.
Bollens, S. ÒPublic Policy and Land Conversion: Lessening Urban Growth Pressure in River Corridors.Ó Growth and Change 21:40-58, 1990.
Gore, J. and Shields, F. ÒCan Large Rivers be Restored?Ó BioScience 45:142-151, 1995.
Larson, L. ÒTough Lessons from Recent Floods.Ó USA Today Magazine 123:33-35, 1994.
Myers, M. and White, G. ÒThe Challenge of the Mississippi Flood.Ó Environment 35:6-20, 1993.
Sparks, R. ÒNeed for Ecosystem Management of Large Rivers and their Flood Plains.Ó BioScience 45:168-182, 1995.
Tarlock, A. ÒInternational Water Law and the Protection of River System Ecosystem Integrity.Ó BYU Journal of Public Law 10:181-211, 1996.
Tibbetts, J. ÒWaterproofing the Midwest.Ó Planning 60:8-13, 1994.
Tripp, J. ÒFlooding: Who is to Blame?Ó USA Today Magazine 123:30-32, 1994.

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