August 10, 2011

Researchers studying Birds Point levee breach

by Tim Crosby

CARBONDALE, Ill. -- When government engineers made the controversial decision to blow holes in the Birds Point levee in southeast Missouri during flooding this spring, researchers at Southern Illinois University Carbondale took note, seeing a unique research opportunity in the unfortunate situation.

The Army Corps of Engineers in May blew a series of breaches in the levee, allowing the Mississippi River to surge across thousands of acres of Missouri farmland.  Officials decided to breach the levee to relieve flooding pressure downstream and protect communities threatened by the serious flooding.

The move, however, caught the interest of James E. Garvey, director of the Fisheries & Illinois Aquaculture Center at SIUC, and Matt Whiles, professor of zoology and director of the SIUC Center for Ecology.  The researchers had long been interested in how the massive levee system aimed at controlling flooding and protecting farms and communities also impacted aquatic life, as well as how well it controls flooding.  Suddenly, with the Birds Point Levee opened up, they had an opportunity to find out.

The National Science Foundation agreed, sending the researchers a quick $78,000 to study how the levee breach, which sent water flooding into nutrient-rich soil, is affecting river life. Two hydrologists from the University of Illinois also will look at water movement issues associated with the levee breach and its subsequent impact on the soil and water in the area.

As flood control approaches go, Garvey said, levees can be a “mixed bag” of successes and failures. Most major rivers in the United States have an extensive levee system, which in some cases has turned slower, wider and more flood-prone rivers into something more like a ditch, Garvey said, with the water tightly channeled and swift moving.

“During most years, if there are moderate years of flow, the levees work fine,” he said.  “The river is contained and people’s property is protected.

“The problem comes with the major events, which we’ve had almost back-to-back in the last couple decades,” he said.  “In those cases, the levees actually make things worse.  They don’t let the water spread out, so it can only go one way.  Once it breaches, there’s nowhere for the water to go so it just piles up and it takes a long time for it to go away.”

Garvey and Whiles want to explore the possibility that incorporating more natural flood plains into the flood control system, as well as moving some levees further away from the river, could provide more effective flood mitigation and promote river production. Garvey theorizes that slowing the water down and allowing it to spread into its natural flood plains -- in this case, heavily fertilized farm fields -- might be a more efficient means of promoting river production.

A lot of it comes down to a simple nutrient: nitrogen, which farmers put in the soil to promote crop growth.

Crops, such as corn, however, are fairly inefficient at pulling out and using the nitrogen placed into the soil by farmers. The leftover nitrogen instead often runs off into streams and ultimately into the river, which carries it south to the Gulf of Mexico where it can cause algae blooms and hypoxia -- a lack of oxygen in the water that kills fish.

If the river floods into those areas and hangs around for a while, however, Garvey and Whiles think the environmental effects will be positive.  The nitrogen will cause algae to grow, which is in turn eaten by zooplankton, insects and invertebrates.  As their numbers increase, so does the food supply for fish and waterfowl populations.

“Nitrogen take-up is very important, and it often has to do with how long the water sits around,” he said.

Flood control would also be enhanced, the researchers theorize, as the water will have a larger area to spread, thus reducing pressure on other levees during major flooding events.

But they acknowledge such an approach, even if scientifically sound, would have to consider economic impacts on all sides, too.

Garvey said the farmland along the river is “extremely valuable” and has a major impact on the economies of several states. Even so, the scientists want to quantify the value of allowing the presence of natural floodplains, both in an economic and ecological sense.

“There’s speculation that it might be better to expose some agricultural land to at least occasional flooding, allowing that water to spread out, than following our current course,” Garvey said.  “The problem is no one is willing to allow that to happen.  As scientists, we’re very interested in finding out what the value of having these as floodplains is.”

River flooding management through levee systems is almost 100 years old in some places, and is used heavily in the middle and lower Mississippi River, Garvey said. Since the federal government instituted the program, however, scientists have learned much more about how rivers work and how they impact life around them.

Garvey hopes to bring some of that new information to bear on the overall issue.

“All we’re looking for is a conversation.  We need to have a conversation about policy,” he said.  “And it needs to be backed up with science.”

At least one graduate student and several undergraduates will benefit from the project, gaining research experience by collecting samples, running tests in laboratories and helping with the data analysis.

Ultimately, Garvey and Whiles would like to get additional grant money to study the long- term effects of the Birds Point levee breach.

“This was really a once-in-a-lifetime, or once-in-a-career opportunity to study this issue,” he said.  “We’re really excited.”