The Cache River Basin, which once drained more than 614,100 acres across six southern Illinois counties, has changed substantively since the ancient Ohio River receded.
The basin contains a slow-moving, meandering river; fertile soils and productive farmlands; deep sand and gravel deposits; sloughs and uplands; and one of the most unique and diverse natural habitats in Illinois and the nation.
According to a recent University of Illinois study, the region's agricultural lands dodged a bullet due to the timing of the great flood of April 2011 when the Ohio River approached the record high of 332.2 feet above sea level.
"The floodwaters eventually drained back into the Ohio River and upper Mississippi River ultimately leaving approximately 1,000 acres of agricultural land flooded from a backup in the middle and lower Cache River Valley, which flooded the adjacent forest-covered alluvial soils and the slightly higher cultivated soils," says U of I researcher Ken Olson.
According to Olson, who has studied the effects of that particular flood extensively, these cultivated soils drained by the middle of June 2011 and were planted to soybeans. The floodwaters left a thin silt and clay deposition on the agricultural lands and crop residue when they receded. These coatings included significant amounts of soil organic carbon, microbes, and pathogens. After the coatings dried, they were incorporated into the topsoil layer of the alluvial soils using tillage equipment.
"Because the flooding occurred during the non-growing season for corn and soybeans, the mixing in of sediment into the topsoil prior to planting resulted in little significant loss of soil productivity, little soybean damage, or yield reduction on lands outside the levees along the Mississippi, Cache, and Ohio rivers," Olson notes.