Rivers: Stemming the Tide

Spring's great tide was flowing again. In Montana and Minnesota, in Illinois and Pennsylvania, the creeks and streams were swollen with melted ice and fresh rains. Into the big rivers they poured, feeding the Ohio, the Missouri and, at last, the Mississippi. In that vast watershed, comprising 41% of the nation's land area and affecting 31 states, spring has always been a season for apprehension—and often of tragedy. Last week, in some few such places as Waterloo, in the Cedar River region of Iowa, where adequate flood-control installations do not yet exist, more than 6,000 people fled their homes as the river overswelled its banks. But for countless other homeowners in the broad center swath of the U.S., the rising tide of spring floodwaters portended no such disaster: they were protected by a fantastic flood-control system that has been abuilding for 135 years at a cost of at least $22 billion.

High in Cairo. The Mississippi's river system is vital. It furnishes power for a huge chunk of U.S. industry. Americans use it to irrigate their farms, to brew beer in Minnesota, to draw off sewage in Ohio and Kentucky, to carry boats and barges over thousands of miles, to help light millions of homes. But the Mississippi, the Ohio and the Missouri, with all their tributaries, are also deadly: in 1952, as an outstanding flood-year example, they cost millions in property damage, along with scores of lives. Now, for the first time in the habitation of North America, the harnessing of the Mississippi system appears in sight.

It has been an awful fight. Until the 1920s, Mississippi basin flood control consisted almost entirely of unconnected local systems. There were lots of them: Cairo, Ill., for example, at the crucial confluence of the Ohio and Mississippi, had dikes that peered down on the city's tallest building. But eventually the U.S. Army Corps of Engineers began working out an integrated flood-control system for the whole river network.

Corn in Percival. The major work picked up impetus after World War II, as the Corps of Engineers divided their labors among several control systems. Dams, reservoirs, floodgates, riprap and levees were built to control the flow rate. Reforestation and soil-conservation practices decreased flood runoff. By enlarging and lining channels, removing snags and other obstructions, and by straightening bends, the engineers reduced flow resistance. Combined with local expenditures, these federal programs will eventually provide for 87 million acre-feet of flood-control storage in 219 reservoirs in the U.S., more than 9,000 miles of levees and floodwalls, and about 7,400 miles of channel improvement (see map).