Mississippi River flood of 1973
The Mississippi River flood of 1973 was a significant natural disaster, marking the highest water levels in the region in over 150 years. Triggered by a combination of heavy rainfall and snowmelt during an unusually warm February, the flood was exacerbated by a saturated drainage basin. By March 1973, flooding conditions emerged along the Missouri River, which contributed to the catastrophic situation. The Army Corps of Engineers had previously implemented flood control measures, including the Low Sill Structure, designed to manage excess water, but the scale of the flooding overwhelmed these systems.
The consequences were severe, with approximately 17 million acres inundated, extensive property damage exceeding $180 million, and over 30 fatalities reported. The disaster left around 35,000 individuals homeless and caused significant ecological harm in the delta region. In response, President Nixon declared all counties along the Mississippi River south of St. Louis as disaster areas. The floodwaters lingered until June, highlighting the challenges of managing such extreme weather events in a historically flood-prone area.
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Subject Terms
Mississippi River flood of 1973
The Event The Mississippi River floods more than seventeen million acres along its valley
Date Began on March 15, 1973
The Mississippi flood left people homeless, killed wildlife, and led President Richard M. Nixon to declare the region a disaster area.
The Mississippi River and its tributaries drain an area of about 3.2 million square kilometers (1.23 million square miles) in the center of the United States. In general, it has its greatest flow in the spring, when snow melts in the drainage basins of the Missouri and Ohio Rivers, and the high discharge from the snowmelt combines with spring precipitation.
In the spring of 1973, the Mississippi River reached its highest level in more than 150 years. The stage for the 1973 flood had been set in the late fall and winter of 1972, when heavy rainfall all along the Mississippi River and its tributaries was followed by equally heavy snowfall in the North and West. The month of February was unusually warm, and the snowmelt collected in a drainage basin that was already saturated. On March 13, following a warm spell that rapidly melted the snow in the northern part of the drainage basin, flooding conditions were reported on the Missouri River. The flooding was worsened by heavy rainfall in which some areas of the drainage basin received more than fourteen inches of rainfall in forty-eight hours.
Because the Mississippi River floods annually, the Army Corps of Engineers had previously built a series of structures that would allow the diversion of excess water to the Atchafalaya River, a shorter route to the Gulf of Mexico. The Low Sill Structure north of Baton Rouge, Louisiana, built of reinforced concrete and comprising eleven floodgates, was part of this system of floodways, levees, and channels connecting the Mississippi and Atchafalaya Rivers. On March 15, a large scour hole began to develop under the Low Sill Structure. Emergency repairs attempted while the river continued at flood levels were not successful, necessitating the first and only opening of the gates at the Morganza Combined Control Structure located about thirty-five miles north of Baton Rouge. The Low Sill Structure was saved, though repairs after the flood cost more than $15 million.
Impact
Unfortunately, the flood control system was overwhelmed by the magnitude of the event, which was the worst flood in the region since 1927. In the lower Mississippi River valley, 17 million acres were inundated, as well as 600,000 acres in the delta. The flood caused more than $180 million in property damage and took a terrible toll on the wildlife living in the delta during the flood. It also left thirty-five thousand people homeless and caused more than thirty deaths. President Nixon declared all of the counties bordering the Mississippi River south of St. Louis, Missouri, as disaster areas. The floodwaters did not completely recede until June.
Bibliography
Ambrose, Stephen E., and Douglas Brinkley. The Mississippi and the Making of a Nation: From the Louisiana Purchase to Today. Washington, D.C.: National Geographic, 2002.
Barry, John M. The Great Mississippi Flood of 1927 and How It Changed America. New York: Touchtone, 1997.