Limiting the impact of future floods.

• Author: Kitch, Harry E.
• Position: Special Section: America Under Water - Cover Story

The flood of 1993 on the Mississippi and Missouri rivers significantly will influence national water resources and environmental policy in much the same way that those of 1927 and 1935 resulted in the Flood Control Acts of 1928 and 1936. These acts established Federal flood protection policy for most of the 20th century.

The damage over a nine-state area has been estimated at as high as $150,000,000,000. The toll on the human spirit from watching homes, businesses, and farms generations old slip beneath the floodwaters can in no way be measured.

Damage could have been far worse if not for the Federal flood control measures in the Lower Missouri,and Upper Mississippi basins. Sixty-six Army Corps of Engineers dams in these basins impounded 15,000,000 acre feet of water that would have increased the downstream levels. The Federal and non-Federal levees and floodwalls that survived the flood provided additional protection, primarily to urban areas. When confronted with rivers swollen by one and a half to three feet of rainfall, over 70% of the more than 1,300 non-Federal levees failed. Two Federal levees gave way and 38 were overtopped, but more than 180 held back the water.

Even as the region began to clean up from the disaster, calls were coming from many segments of the population urging that the approach to dealing with floods be reconsidered. Before doing so, it is necessary to understand how these basins were developed by looking at their histories.

On the Lower Mississippi River, repeated high water events created natural levees, behind which lowlands stretched for miles. When a flood topped or broke through these levees, it spread out over the vast lowlands, creating a shallow, but expansive, flood. Before the Civil War, lowland residents started raising the natural levees. At first, those people closest to the river undertook this work. As those farther inland also benefited from the levees and suffered from their failure or absence, lowland residents banded together and formed levee districts or unions to build and maintain them.

Meanwhile, on the Upper Mississippi River north of Rock Island, Ill., few such levees exist. There, farmlands and towns lie within a narrow valley defined by high, steep bluffs. In this valley, the water could not spread out as it did on the lower river, and fewer people were affected by floods.

Organized Federal involvement in the Lower Mississippi Basin began when Congress authorized a topographical and hydrographic survey of the Lower Mississippi River that was completed in 186 1. In 1879, it established the Mississippi River Commission (MRC) to respond to a need for improvement of the Lower Mississippi River and coordination of engineering operations through a centralized organization. The MRC was charged with protecting the banks of the Lower Mississippi, with emphasis on channel stabilization and navigation, rather than development of flood control works.

In early 1927, the most disastrous flood in recorded history of the Lower Mississippi occurred, breaching numerous levees and...