Dr. Frank Heitmuller, associate professor of geography and geology at The University of Southern Mississippi, says the devastation wrought by the recent Mississippi River flooding should come as no great surprise.
“We develop our infrastructure in locations where floods, storm surges, fires, etc. are not just likely to occur, but are expected to occur,” said Heitmuller, who specializes in surface-water hydrology and sedimentology. “The biggest question is: how much are we willing to subsidize people and infrastructure via insurance and government programs in areas prone to natural hazards?”
Heitmuller recent returned from a reconnaissance trip to the lower Mississippi River region where he assessed the flooding and associated flood-control structures such as levees and spillways.
The river has been steadily rising over the past several weeks following heavy spring trains in the upper Mississippi Valley. Thousands of residents from Memphis, Tenn., to Baton Rouge, La., have been displaced by the floodwaters. In Vicksburg, Miss., the river reached a crest of 57.1 feet on Thursday, May 19, well above the 53.2 feet recorded in 1937 and the 56.2 mark set during the Great Flood of 1927. The murky water engulfing homes near the river is not expected to recede for several more weeks.
Heitmuller notes that a large flood of this magnitude is expected to occur periodically. He explains that the definition of a “100-year-flood” is a maximum flow of water (cubic feet per second) that has a one percent statistical chance of happening each year. He further points out that floods of this proportion can produce benefits not apparent at first glance.
“Although the flood is terrible for homes and businesses in its path, it is also a natural process that can remediate considerable environmental problems like wetland loss in Louisiana, riparian ecology and the associated economics of oyster, shrimp and crawfish harvesting,” said Heitmuller.
He added that temporary negative effects to the shellfish industry in Louisiana will be apparent with the influx of freshwater. However, the long-term effects of sediment transport to wetlands are beneficial for the seafood industry.
Heitmuller suggests the United States become more progressive about flood control by examining countries such as The Netherlands, where the “Room for the River” program along the Rhine River is being implemented. That initiative is designed to move flood-control levees back further from the river and excavate the floodplain surface between the new levee location and the riverbank.
“One big problem we have along the Lower Mississippi and other rivers that are being controlled by levees in this country is that little room is available for the floodwaters to be stored,” he said. “Furthermore, the ‘job’ of a river is to move all of the sediment, not just the water. In some cases, floodplains between levees are growing ‘upward’ because sediment is being deposited at an artificially rapid rate instead of being able to be spread out over a larger area.”
And the consequences have been dramatic. “The result is an increasing risk of levee failure and flooding catastrophe because there is less and less room to convey the floodwaters,” he said.