Olson cautioned that, had winter wheat been planted outside the levees in the fall of 2010, the wheat crop would have drowned. “Illinois farmers are aware of the flooding potential, especially in the winter and early spring, so they don’t plant winter wheat on unprotected bottomlands,” he said. “Consequently, there was no crop loss outside the levees in April and May of 2011. Local floodwater in the lower Cache River Valley, south of the Mississippi River Diversion and Dike, could not flow back into the Ohio River. It was blocked by the Cache River levee on the south side and by the closed gate at the Ohio River levee. Instead, water backed up and flooded forested and agricultural lands along the lower Cache River and north of the Cache River levee,” Olson said.
Olson said that the damage to the land could have been much worse. “Land use changes, diversion ditches and levees, loss of wetlands and flood-holding capacity, internal channelization of the Cache River and tributaries, and an ever-changing climate have altered the hydrology of the valley, redistributed soil from fields and ditch banks into the river, and transported tons of sediment during flooding events into both the Ohio and Mississippi rivers,” Olson said.
As the 2011 Ohio River floodwater reclaimed its ancient floodway, Olson says that the extent of these hydrologic changes and their social, economic, and environmental impacts have become more apparent. “The Great Flood of 2011 lends urgency to the reevaluation and implementation of the Cache River Watershed Resource Plan completed in 1995,” Olson said.
He cited nine resource concerns that were identified: erosion, open dumping, private property rights, water quality, continuation of government farm conservation programs, Post Creek Cutoff stream bank erosion, open flow on the Cache River, dissemination of accurate and timely information throughout the watershed, and the impacts of wildlife on farming and vice versa.
“Most of these concerns still need to be addressed,” Olson said. “Since that plan was created, there have been additional compromises/breaches that need to be repaired. As the repair and rebuilding of the valley infrastructure is undertaken, there will need to be a significant investment of human and financial resources to reduce the impacts of future catastrophic events.”
“The 2011 Ohio River flooding of the Cache River Valley in southern Illinois,” which was co-authored by Kenneth R. Olson and Lois Wright Morton, was published in a 2014 issue of the Journal of Soil and Water Conservation and can be found online at http://www.jswconline.org/content/69/1/5A.full.pdf+html.