- Date:
- April 2011 - May 2011
Mississippi River flood of 2011
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What was the Mississippi River flood of 2011?
The Mississippi River flood of 2011 was a significant flood event in the central United States, comparable to the floods of 1927 and 1937. Heavy rain and snowmelt led to swelling tributaries and the Mississippi River itself in April 2011.
Managed by the U.S. Army Corps of Engineers, a system of levees and spillways helped channel floodwaters, but breaches in Missouri, Arkansas, Mississippi, and Tennessee still caused the evacuation of thousands. The demolition of a levee in Missouri spared Cairo, Illinois, but flooded 200 square miles of farmland. Spillways were opened in Louisiana to protect Baton Rouge and New Orleans, diverting water into Lake Pontchartrain and the Atchafalaya River basin.
The flood disrupted commerce, including grain shipping, and raised concerns about the long-term effects on cropland and water quality in the Gulf of Mexico.
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Where did the flood occur along the Mississippi River?
The Mississippi River flood of 2011, comparable to the floods of 1927 and 1937, submerged thousands of square miles of land in the central United States. From late April to May 2011, the flood impacted states such as Missouri, Arkansas, Mississippi, and Tennessee, causing levee breaches and the displacement of thousands of people.
To prevent inundation of larger settlements, officials opened spillways and, in some cases, purposely breached levees, such as in Missouri to save Cairo, Illinois. Concerns for cities like Baton Rouge and New Orleans in Louisiana led to the opening of spillways, diverting water into Lake Pontchartrain and the Atchafalaya River basin.
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What caused the Mississippi River to flood in 2011?
The Mississippi River flood of 2011 was caused by heavy rain and snowmelt in late winter and early spring, which led to swelling tributaries and, consequently, the river itself. The scale of flooding had not been seen since 1927 and 1937.
To manage the torrent, the U.S. Army Corps of Engineers used a system of levees and spillways to channel floodwaters. The decision to breach levees in Missouri prevented the Illinois town of Cairo from flooding, but it also resulted in the submergence of 200 square miles of farmland. Concerns about potential levee breaches near Baton Rouge and New Orleans led to the opening of spillways.
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How did the flood affect people and communities in the area?
The Mississippi River flood of 2011 had a profound impact on people and communities. Thousands were forced to flee as levees breached in Missouri, Arkansas, Mississippi, and Tennessee. Fatalities were limited to a few people who drowned in flash floods.
To prevent the inundation of Cairo, Illinois, a levee was demolished in Missouri, which resulted in the submergence of 200 square miles (520 square km) of farmland. Concerns about potential levee breaches in Baton Rouge and New Orleans led to the opening of spillways, which caused the evacuation of nearly 3,500 people and the covering of approximately 3,000 square miles (7,770 square km), much of it cropland, in the Atchafalaya River basin.
The flood also disrupted commerce with the closure of a main grain-shipping port. As the waters receded, many properties were condemned, and the fate of submerged cropland remained uncertain due to debris, bacteria, and chemicals.
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What steps did the government take to control or manage the flood?
In response to the Mississippi River flood of 2011, the government took several steps to manage the disaster. The U.S. Army Corps of Engineers managed a system of levees and spillways to contain and channel floodwaters, which helped state officials to reinforce existing structures and evacuate residents.
To prevent inundation of larger cities, officials opened the Bonnet Carre Spillway north of New Orleans and the Morganza Spillway north of Baton Rouge, diverting water into Lake Pontchartrain and the Atchafalaya River basin. The flood-control target has become an integrated system able to master a "project flood," the largest theoretical flood expected along the river.
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What lasting impacts did the Mississippi River flood of 2011 have on the region?
The Mississippi River flood of 2011 had wide-ranging, enduring impacts. Thousands were displaced in states like Missouri, Arkansas, and Mississippi due to levee breaches. Approximately 3,500 people were evacuated when spillways opened in Louisiana to protect Baton Rouge and New Orleans. Commerce suffered with the closure of grain-shipping ports.
The floodwaters deposited debris and bacteria on properties and cropland, and many properties were condemned. Chemicals amplified the Gulf of Mexico's dead zone, harming fisheries already reeling from the Deepwater Horizon oil spill. The flood also prompted a review of flood-control management, with more consideration given to limiting land use in flood-prone areas.
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Mississippi River flood of 2011, flooding of the Mississippi River valley in the central United States from late April to May 2011 on a scale not seen since the floods of 1927 and 1937. Thousands of square miles of agricultural and residential land were submerged by water that had surged over the banks of the Mississippi River system or that had been purposely diverted from large settlements through the blasting of levees and the opening of spillways.
The late winter and early spring of 2011 were filled with snowmelt and heavy rain events—including the Tornado Super Outbreak of 2011. As a result, the tributaries of the Mississippi and, consequently, the river itself began to swell in April. Because previous floods—particularly the Great Flood of 1927—had catalyzed the construction of numerous levees and spillways to contain and channel floodwaters, the path of the torrent was to a certain extent predictable and controllable. That system, managed by the U.S. Army Corps of Engineers, assisted in determining approximately when and where the water would breach its banks and thus enabled state officials to shore up existing structures and evacuate residents.
The breach of levees in Missouri, Arkansas, Mississippi, and Tennessee precipitated the flight of thousands, though fatalities were restricted to several people who drowned in flash floods and flooding of tributaries in Arkansas in late April and an elderly man in Mississippi in May. The May 2 demolition of portions of a levee in Missouri prevented the inundation of the small Illinois town of Cairo, though the diverted water immersed 200 square miles (520 square km) of farmland.
Concerns that the levees could be breached in the Louisiana cities of Baton Rouge and New Orleans—displacing thousands of people and shutting down a network of petroleum refineries that accounted for a substantial portion of domestic gasoline production—led to the opening of two spillways in May. With waters approaching the 1.25 million cubic feet (35,000 cubic metres) per second rate that indicated a possible risk to the cities, on May 9 the Bonnet Carre Spillway, approximately 30 miles (50 km) north of New Orleans, was partially opened, allowing overflow into Lake Pontchartrain, which drains into the Gulf of Mexico. Further channels were opened the following days. On May 14 the Morganza Spillway, about 35 miles (56 km) north of Baton Rouge, was partially opened, with more channels opened in the ensuing days. Nearly 3,500 people were evacuated. Those waters drained into the Atchafalaya River basin, covering some 3,000 square miles (7,770 square km), much of it cropland.
The effects of the flood extended beyond the exigencies of channeling water and relocating people in its path. The closure of a main grain-shipping port, Natchez, Miss., on May 16, sparked fears of the flood’s effect on commerce; the port was reopened shortly thereafter on a limited basis. Major shipments of coal from New Orleans were also delayed.
In the latter weeks of May, as the Mississippi River crested at record levels in many areas and then began to slowly recede, state officials began the process of evaluating evacuated properties for habitability. Many were condemned or would need to be gutted. The fate of cropland that had been immersed by floodwaters was uncertain. Though historically the residual silt from such floods boosted soil nutrients, the passage of the water through agricultural and residential areas led to the deposition of debris and bacteria. Chemicals that had entered the waterway amplified the already-prodigious effects of agriculture on the Gulf of Mexico, which has long suffered from an extensive dead zone caused by fertilizer-fed algae blooms that deoxygenate the water. The expansion of that zone with the increased fertilizer load would wreak havoc on fisheries already suffering because of the effects of the Deepwater Horizon oil spill of 2010.