UM Institute Assisting State Agency with Flood Mitigation Plan

This map, created by the Mississippi Mineral Resources, Institute shows different vulnerabilities to flooding in the Yazoo Basin. (Photo courtesy of MMRI)

As emergency responders cope with breached levees along the upper Mississippi River, geologists at the University of Mississippi recently submitted their assessment of which areas of the Mississippi Delta would be affected most by future floodwaters.

The Mississippi Delta Flood Mitigation Project was conducted by university’s Mississippi Mineral Resources Institute, known as MMRI, for the Mississippi Emergency Management Agency after the latter received federal funds.

Ole Miss scientists were tasked with determining the locations and conditions of all levees in the Yazoo Basin area, along with the critical facilities – such as hospitals, schools, utility infrastructure and government buildings – in each community.

“Should floods occur, MEMA wants to know where those things are,” said Charles Swann, associate director of MMRI. “We created and gave them a lot of maps depicting these things – not only along the Mississippi River, but along the Coldwater and Yazoo Rivers as well.”

The MMRI study considered all components of vulnerability, expressed as social, economic, environmental and physical indicators. These were combined into a Flood Vulnerability Index, ranked on the relative degree of vulnerability as either low, moderate or high.

The high FVI category represents the susceptibility to long-term social and economic loss. The moderate category represents the susceptibility to short-term agricultural loss. The low category represents areas less susceptible to flooding as a whole, although if these areas flood, they could experience significant social and economic losses.

The Yazoo Basin comprises an area of 4.6 million acres (about 7,232 square miles). The study revealed that of that area, 75 percent ranked low, 24 percent was moderate and only 1 percent is considered at high risk.

“Some areas are more vulnerable to flooding than others,” said Louis Zachos, UM assistant professor of geology and geological engineering and a co-investigator with Swann. “For example, people living in Issaquena and Warren counties are experiencing backwater floods right now because they live in front of the levees instead of behind them. There’s nothing between them and the river to protect them.”

MMRI contacted the National Center for Computational Hydroscience and Engineering, also at Ole Miss, to create computational models of how a catastrophic flood event would impact the Delta region. Engineers chose 28 points along the river levee to model these hypothetical floods. These models depict how rising water might flow through the Delta for a 10-day period.

“The NCCHE models confirmed our own mapped predictions,” Swann said. “The irony is that the models demonstrate floodwaters don’t always go where your logic says that they should.”

Depending upon the severity of flooding, the number of potential victims could range from a few thousand to tens of thousands, Zachos said.

“Hopefully, as federal and state funds are allotted and released within the next year, MEMA can use all these data to create a proposal showing flood mitigation needs to be a priority,” he said.

Swann agreed.

To view MMRI geologists discussing flood mitigation with MEMA officials, click on link.

“There’s definitely a window of opportunity that needs to be stepped into here,” he said. “Funding should be made available before disasters come, not just afterward. The best time to apply for funding is right after something has happened and while it’s still on people’s minds.”

The Yazoo Basin has historically been defined by flooding. The flood of 2011 was a warning that a repeat of the catastrophic floods of 1927 is possible.

“Without adequate planning, the loss of life and property would exceed the losses of 1927 by many times,” Zachos said. “The validity of the vulnerability indices is verified by detailed modeling of catastrophic flooding events.”

And MEMA should consider more than just possible breaches in the mainline levees.

“A levee break is not the only source of flooding in the Yazoo Basin,” Zachos said. “Several major tributaries entering the basin have upstream earthen dams that could release large volumes of water, resulting from significant rain events that could also lead to catastrophic flooding. The calculations we provided apply equally to flooding from any source and can be used to evaluate vulnerability to flooding from these or any other events.”

For more information about the MMRI, visit http://mmri.olemiss.edu/Home.aspx.

Courtesy of Edwin Smith and the Ole Miss News Desk