The 2011 Ohio River flooding of the Cache River Valley in southern Illinois

Excerpt

In late April and early May of 2011, the Ohio River briefly reclaimed its ancient floodway through southern Illinois to the Mississippi River as heavy rains and early snowmelt over the eastern Ohio Basin raised the Ohio River gage at Cairo, Illinois, to 18.7 m (61.72 ft) (NOAA 2012). The Cache River Valley, carved by the ancient Ohio River prior to the last glacial period approximately 14,000 years ago, once again filled with a torrent of waters as the Ohio River at flood stage pushed into and reversed the flow of the Post Creek Cutoff, a diversionary ditch designed to drain wetlands for agriculture (figure 1). Concurrently, the Mississippi River on the western edge of the valley was backed up and threatened the integrity of the Len Small and Fayville levee systems to protect agricultural lands, Horseshoe Lake, homes, and rural towns (Olson and Morton 2013a). As Ohio River floodwaters rushed into the Main Ditch from the east, the rain-swollen, meandering Cache River and the extensive drainage systems throughout the valley, already filled to capacity, overflowed the internal system of levees and flooded Massac, Pulaski, and Alexander counties as far west as Olive Branch and Horseshoe Lake. To explain the…