Sinkholes and sand boils during 2011 record flooding in Cairo, Illinois

Abstract

T he southwestern tip of Illinois is bounded by the Mississippi and Ohio rivers, which converge at Cairo (figure 1), a river city with a long history of steamboats, barges, railroads, and road bridges spanning three states. The physical, economic, and social reconstruction of this flood-prone peninsula following the evacuation of the entire city on May 1, 2011, challenged local residents, community leaders, and the US Army Corps of Engineers (USACE) to strengthen levees, repair roads and bridges, and strengthen other basic infrastructure. While the Cairo floodwall and levee system was able to withstand the record-breaking flood of 2011 (NOAA 2012), it took more than two years for sand boils and sinkholes to be repaired. By the fall of 2013, the weakened levees and the flood-wall were reengineered and strengthened in preparation for future flood events. THE OHIO AND MISSISSIPPI RIVERS Cairo has a history of battling two rivers that are its economic lifeblood and also its greatest source of unease and vulnerability. The approximately 4,000 ha (10,000 ac) between the Ohio and Mississippi rivers where the city is located today were originally an 1818 land trust owned by land speculator investors from New York City and Philadelphia (Lansden 1910). The…