Thursday, May 19, 2011

The Mississippi River and the Sustainability of the “American” Approach

For weeks we have watched as heavy spring storms and winter snow melt have combined to raise the Mississippi beyond flood levels. The crest of the flood waters has rolled down the Mississippi River, a natural disaster in slow motion. To prevent the breach of the levee system protecting the cities and towns along the river the U.S. Army Corps of Engineers have activated the approved and existing flood control plan which is to protect the levee system and cities by opening the open the Bonnet Carré Spillway and the Morganza Floodway in Louisiana after blasting a 2-mile-wide hole in a levee in Missouri to open a floodway, dropping water levels but also submerging 130,000 acres of prime farmland. Crops are flooded, homes are lost, the small towns sacrificed to the cities. It is sad to contemplate the loss these families have experienced; nonetheless, New Orleans and Baton Rouge remain dry and the levee system intact. When the flood waters recede, commerce on the Mississippi will resume.

The Mississippi River has the third largest drainage basin in the world, after the Amazon and Congo Rivers. It is reported to drain more than 1,245,000 square miles, and includes all or parts of 31 states and two Canadian provinces. Waters from as far east as New York and as far west as Montana contribute to flows in the lower river. The Mississippi is a navigation artery of great importance to the nation's transportation system, carrying an ever-growing commerce in a cost effective and sustainable way. In addition the River supplies water for the cities and industries that have located along its banks.

Major floods of the Mississippi have occurred in 1882, 1912, 1913, 1927, and 1937. The flood of 1927 was the most disastrous in the history of the Lower Mississippi Valley. An area of about 26,000 square miles was inundated. Levees were breached, and cities, towns, and farms were laid to waste. Crops were destroyed, and industries and transportation paralyzed. Over the next decades the flood control system and flood control plan to activate during times of excessive river flow when the system is endangered was developed. The whole goal of this system was to protect the cities and the shipping channel from destruction.

The four major elements of the Mississippi River and Tributaries flood control system are: levees for containing flood flows; floodways which serve as relief valves for excess river flow but sacrifice a 5 mile wide strip of land adjacent to the Mississippi primary levee; channel improvement and stabilization for stabilizing the channel against the forces of turbulent flow and sediment movement in order to provide a navigable channel for commerce, and for protection of the levees system; and tributary basin improvements for major drainage and for flood control, such as dams and reservoirs, pumping plants, and emergency channels., and the like. This system serves to protect, but also tries to freeze the Mississippi shipping channel from geologic change. Over thousand of years, the lower portion of the Mississippi River has used different pathways as its main channel to the Gulf of Mexico across the delta region. Left to the natural forces of nature, a new main channel will form through river avulsion. However, the management of the flood control system has prevented this from happening.

The flood control system has worked for decades, but the price of the flood control system is high, to save the cities, towns, refineries and the shipping channel mean controlling the flow of the river. This record breaking flood caught the U.S. Army Corp of Engineers in the process of obtaining approval for changing its approach to flood management. For decades, the agency has focused on preventing floods, with the Mississippi flood-control system dating to the aftermath of the great flood of 1927. This summer, it expects to win federal approval for a policy it has begun phasing in over the past several years: allowing more flooding to occur, while working with local and state governments to manage development on surrounding land to reduce economic damage and loss when a flood happens.

In recent years, the goal has been to manage development on the flood plane. There are practical, engineering and cost limitations to being entirely dependent on a levee system that effectively channels all flow towards the river. There are limitations. The idea is not to dismantle the levee structures, but to use other techniques to prevent the river from getting so high. A natural flood plain would serve to absorb the storm surges. The problem in executing this kind of approach is maintaining a natural flood plain. In the twentieth century, building an impenetrable levee at any cost seemed possible and in truth it was easier to spend Federal funds rather than battle the political and lobbying forces to control development, but levees need to be maintained and expanded with continued population growth and we do not plan, save or build for what the Army Corp of Engineers calls the “project flood” that we are experiencing now. Instead we have depended on the US have the resources to evacuate before the flood and then restore. Limitations on development of privately owned land have always been a tough sell in the United States; however, the challenges and costs look different in the twenty first century.

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