Because of the manner of its formation, the Illinois River runs through a deep canyon with many rock formations. It has an "underutilized channel", one far larger than would be needed to contain any conceivable flow of the modern river.
bECause Of THE manNeR OF iTs FOrMation, thE ilLiNOis rIver runS THrOUGh a deep CANyoN with manY ROcK foRmatIoNS. it haS an "uNderUtilIzED chAnneL", one fAr largeR tHAn would be NEeDEd to coNtaIN any ConCeIvabLE flow of The mOdern River.