Levee detonations reduced 2011 flood risk on Mississippi River, study finds

March 20, 2015, University of California, Irvine

A controversial decision in 2011 to blow up Mississippi River levees reduced the risk of flooding in a city upstream, lowering the height of the rain-swollen river just before it reached its peak, according to a newly published computer modeling analysis led by UC Irvine scientists.

The work focused on a Missouri agricultural area called the New Madrid Floodway that was inundated when the levees were detonated. The researchers found that the region would have flooded anyway if the river had been allowed to overtop the levee banks. And separate modeling showed that the resulting damage to crops and buildings would have been similar either way, though the detonations did shift the damage zone toward Missouri and away from Illinois and Kentucky.

Previous studies had reported more than $50 million in levee repair costs as well as damage solely from the rapid flow of water across the floodway after the detonations, which scoured farmland and left behind thick deposits of unwanted sand. The new research found that allowing those levees to overtop naturally would have resulted in less erosion.

Still, the flood risk was reduced for the upstream city - Cairo, Ill. - just as intended.

"Our model's not saying the water would have definitely overtopped the levees at Cairo," said UCI professor and chair of civil & environmental engineering Brett Sanders, an author of the study led by UCI graduate student Adam Luke. "It doesn't say it wouldn't have happened. What we're saying is that reduced the risk of flooding."

Luke built a computer model of the devastating 2011 floods along the Mississippi and Ohio rivers. Then he compared modeling runs conducted both with and without the levee detonations. He discovered that they resulted in a lowering of Mississippi River levels near Cairo by 2.6 feet.

The team also used a separate developed by the Federal Emergency Management Agency to estimate the costs: more than $250 million in building and crop damage in the flooded area. That's about $11 million less than it would have been had the levees not been detonated but allowed to overtop without intervention.

The study's findings support earlier work showing the erosion of flood plains caused by levee bursts, leaving scour holes and sand deposits. With that being a potentially major drawback to flood control by detonation, the authors recommend that engineers place greater emphasis on minimizing erosion when creating such a flood control system.

"Can we design these breaches so there is less scouring and erosion, so we don't get deposits of sand that require millions of dollars to repair?" Sanders asked.

Brad Kaplan, Jeremiah Lant and Doug Alsdorf of The Ohio State University and Paul Bates and Jeff Neal of the United Kingdom's University of Bristol also contributed to the study, which was published online March 8 in the science journal Natural Hazards.

Explore further: Effects of flooding on Cairo, Ill.

Related Stories

Effects of flooding on Cairo, Ill.

March 9, 2012

When faced with a choice between a deluge or a controlled deluge in May 2011 that would protect the city of Cairo, Illinois, the U.S. Army Corps of Engineers chose the latter by ordering an intentional breach of the Mississippi ...

Rescuing farmland after a flood

January 13, 2015

When levees fail, either naturally or as an intentional breach, as was the case on the Mississippi River in 2011, an orchestrated effort is made to remove or repair flood-damaged homes and other structures. A University of ...

Study of 2011 flood will lead to better preparedness

February 18, 2014

In May 2011, when the U.S. Army Corps of Engineers used explosives to breach a levee south of Cairo, Ill., diverting the rising waters of the Mississippi and Ohio rivers to prevent flooding in the town, about 130,000 acres ...

Recommended for you

Oceans of garbage prompt war on plastics

December 15, 2018

Faced with images of turtles smothered by plastic bags, beaches carpeted with garbage and islands of trash floating in the oceans, environmentalists say the world is waking up to the need to tackle plastic pollution at the ...

A damming trend

December 14, 2018

Hundreds of dams are being proposed for Mekong River basin in Southeast Asia. The negative social and environmental consequences—affecting everything from food security to the environment—greatly outweigh the positive ...

The long dry: global water supplies are shrinking

December 13, 2018

A global study has found a paradox: our water supplies are shrinking at the same time as climate change is generating more intense rain. And the culprit is the drying of soils, say researchers, pointing to a world where drought-like ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.