Far and Wide: The Omaha-Council Bluffs Levees and the Flood of 2011

In 2011, an ocean of water poured down the Missouri River from the Dakotas and Montana.  The deluge represented the largest flood to strike the Missouri Valley since 1952.

At the peak of that earlier flood on April 18, 1952, the Missouri hurled 396,000 cubic feet per second past Omaha-Council Bluffs.  From Sioux City to the mouth of the Kaw River at Kansas City, the swollen river stretched from valley wall to valley wall – completely inundating the bottomlands.  A yellow, inland sea sank farmsteads, cropland, and rural roadways.  Since suburban housing developments and industrial parks did not yet exist in the river’s floodplain, high water devastated mostly agricultural land. Consequently, farmers bore the brunt of the financial losses associated with that flood.  Damage estimates ran as high as $179 million (or $1.48 billion in today’s dollars).

At  the height of this year’s flood on July 2nd, the Missouri shoved 212,000 cubic feet per second past Omaha-Council Bluffs.  Even though the maximum volume of floodwater in 2011 equaled a little over half of the peak flow of 1952, the Missouri still achieved an impressive width through western Iowa, eastern Nebraska, eastern Kansas, and northwestern Missouri.  Near the town of Missouri Valley, Iowa, the river extended approximately eleven miles from the Nebraska bluffs to the Loess Hills of Iowa.  A number of factors contributed to the Missouri’s great width, not the least of which was the high volume of water exiting Gavin’s Point Dam.  However, previous human manipulation of the valley environment contributed to the spread of the floodwaters in 2011.

From 1891 to 1981, the Army channelized 753 miles of the Lower Missouri between Ponca, Nebraska, and the river’s mouth.  Channelization structures narrowed, straightened, and quickened the once wide, winding, slow stream.  In 2011, the Army’s 8,300 pile dikes and revetments prevented the Missouri from entering its former floodplain and naturally reducing its flood crest.  Denied access to its old channel areas, the Missouri was forced up and out – way out.  Once it overtopped its man-made banks, the fast-moving river quickly spread its thick, dark waters over the lowlands.

In the late nineteenth century, and throughout the twentieth century, farmers drained the Missouri Valley’s wetlands, oxbows lakes, and low-lying areas to increase their crop acreage.  They also laser-leveled segments of the valley, removing even slight undulations.  These actions destroyed the water storage capacity of the lower valley.  By 2011, there existed few natural depressions in the valley to hold floodwater or slow its forward momentum.  Consequently, the 2011 deluge moved further afield than it otherwise would have had portions of the old, undulating valley floor still existed.

Contrary to the beliefs of many valley residents, levees do not prevent flooding.  As a matter of fact, they can worsen flooding. We only need to look at the Army’s experience along the Mississippi River to recognize that levees have not halted flooding along that big river.  Obviously, levees protect some land.  But water has to go somewhere.  If it is stopped by a levee, it will move elsewhere – usually onto land that does not possess a levee.

After the 1952 flood, the people of Omaha-Council Bluffs built levees to protect their property from the Missouri.  The levees allowed for the construction of businesses in the river’s former floodplain.  Casinos, car lots, an assortment of retail shops, and an interstate highway now stand where the Missouri once flowed.  In 2011, the levees spared Omaha-Council Bluffs from a catastrophic inundation.  But those same levees exacerbated flooding north of those two cities.

In early June, the Mighty Mo pushed heavily against the levees built on the Iowa and Nebraska side of the river at Omaha-Council Bluffs.  Unable to move all of its water through the tight funnel that is the Missouri River at Omaha-Council Bluffs, the river backed up, inundating Interstate-29, Interstate-680, and thousands of acres of agricultural land.  If one needs confirmation of this fact, look at NASA’s satellite image of the Omaha-Council Bluffs metroplex during the flood.  The image clearly shows the Missouri being backed up by the levee located between the two cities.

The Army Corps of Engineers recently received hundreds of millions of dollars for repair work along the Missouri River.  According to Brigadier General John McMahon, the Army plans on spending the money rebuilding the very same hydraulic systems that contributed to the flood – including the navigation channel and the levees located next to the river.  This course of action may be expedient for the Army and its congressional backers, but it is a grave mistake.  Valley residents should demand that the federal dollars be spent to dismantle the navigation channel, reconnect the river to its former floodplain, modify the alignment of levees that contribute to high water levels in nearby areas, and reestablish the Lower Missouri’s water storage capacity by recreating wetlands.  If those actions are not taken, we can expect the Missouri to again spread far and wide across its valley during the next flood.

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