Mitigating farm land flood damage
Last summer's Mississippi River flooding that included the deliberate breach of a levee in southern Illinois and Missouri may have started irreversible change to that region's landscape and its potential as farm land.
That's Kenneth Olson's take. The University of Illinois soil scientist and conservation specialist says the most poignant change happened when the U.S. Army Corps of Engineers was granted authority to open the New Madrid Floodway that eventually overtook the Birds Point, Missouri, levee and flooded an area of more than 130,000 acres. When the levee breached, the river -- and the effect of the resulting output -- was higher than expeted.
“The initial additional force and depth of floodwater caused more damage to buildings and more deep land scouring than was predicted," Olson says. "The strong current and sweep of water through the Birds Point, Missouri, breach created deep gullies in 133,000 acres of Missouri farmland, displaced tons of soil, and damaged irrigation equipment, farms and homes.”
The initial effect was one thing. But now, the longer-term ramifications to the area's farm land is an altogether different one. Olson says though the water's receded, the land that's left has been difficult to repair, and some may be irreparable. Either way, the area's potential farm productivity has been altered.
"Proper drainage in the area has been restored, but the unanticipated fields with large and deep gullies located five miles from the levee breaches will not be repaired very easily," he says. "The resulting land surface will have less soil aggregation, less organic carbon, and be more sloping, making it difficult to farm the land.
"Most remaining terraces, contour farming, strip cropping, and waterways were effective. But many waterways were filled above capacity and were eroded by fast-moving water or had significant sediment depositions," Olson adds.
What if this all happens again? Olson says there are some changes, regardless of the land's composition in the affected area, that could ease the effects of another disastrous flood. Planting more forage crops in uplands, using more adjacent land for timber or grass and adding water storage capacity to the floodplain could help. In general, Olson says looking at the floodplain land as a functional part of a flood mitigation system helps, too.
"It would also be logical to accept periodic levee breaks or stop using the floodplain soil for agricultural crop production," he says. "Instead the land could be converted to conservation use and restore the periodic water storage function to the natural floodplain."