2011 Flood

*** Mississippi Levee Board Conversation (Podcast) ***

The 2011 Flood was a historical event all along the Lower Mississippi River. The 2011 Flood was a multi-hundred year event on the Mississippi River with the crest being 3.2' above the 100-year flood. The fact that the levee contained the 2011 Flood Event limiting the flooding to the riverside and no flooding occurred on the protected side of the levee was a tremendous success story. The 2011 crest was 6' above 1973 crest and, depending on the gage location, broke or came very close to breaking the 1927 & 1937 record levels. A total of 2.272 million cubic feet per sec (mcfs) flowed past Vicksburg at the crest. The flow of the Mississippi River during the 2011 Flood broke all previous record flows. In 2011 the MR&T levees protected 4.1 million people and prevented 10 million acres from being flooded and prevented $108 billion in damages.

2011 Weather Patterns: How Did This Happen?

On February 22 the Mississippi River at the Greenville gage was 17.3'. This stage was 12' below average for this time of year. A massive rainfall event over the Ohio River system combined with the snow melt caused a very sharp rise in the Mississippi River. In 10 days the Greenville Gage rose 20.5' to stage 37.8'. The Greenville Gage crested on March 29th at 48.8'. By April 13 Greenville dropped to 40.2'. Then rainfall events 600 percent to 1000 percent above average over a two–week period over the entire Mississippi River Valley occurred and the Greenville Gage was forecast to reach 65'. Luckily, over the next few weeks leading up to the crest there was very little rainfall over the Mississippi River Valley. This dry weather kept us from reaching a crest closer to the Project Design Flood (PDF). The PDF for the Greenville Gage is 72.2'. The Mississippi River at Greenville crested at 64.2' on May 17th which is 8' below the PDF.

MR&T Project Fully Implemented

Following the devastating 1927 Flood, the U.S. Congress passed the 1928 Flood Control Act, which authorized and created the Mississippi River & Tributaries Project (MR&T). The MR&T Project includes uniform levees, floodways, channel improvements and major tributary improvements. 2011 was the first year where all the features of the MR&T Project had to be utilized at the same time. The Birds Point/New Madrid Levee was intentionally breached by the U.S. Army Corps of Engineers (Corps) on May 6, 2011 at 61.0' at the Cairo Gage. The only other time in history the Corps blew this levee was in 1937. This was done to save the city of Cairo, IL. This feature did not help the Mississippi Levee District. In Kentucky both the Kentucky Dam along the Tennessee River and Barkley Dam along the Cumberland River were filled to maximum capacity in order to reduce the flow into the Mississippi River. The Old River Control Structure was operated and it helps maintain a 70/30 latitude flow between the Mississippi River and the Atchafalaya River. The Bonnet Carre Spillway was operated on May 9, 2011, when the flow in the Mississippi River reached 1,250,000 cfs. The Morganza Floodway was opened on May 14, 2011, when the flow in the Mississippi River reached 1,500,000 cfs. The only other time in history this floodway was opened was in 1973. All three of these floodways were opened to save Baton Rouge and New Orleans, L.A. The operation of these three floodways did not help the Mississippi Levee District.

Summary

The 2011 Flood is the new benchmark highwater event that will be used from this point forward. The safe passage of this multi-hundred year event is a testament to the daily maintenance activities of the Levee Board Staff and Crew, the Levee Board Commissioners leadership and dedication to flood control for the Mississippi Delta, Congress’s yearly wise appropriations for construction and maintenance for the MR&T Project, and the Corps of Engineers vision, foresight, engineering and construction. Those involved in this event will remember the 2011 Flood for the rest of their lives. All these people were needed, much appreciated and heros for the Mississippi Delta.