Ecosystem Response to Bird's Point Levee Breach

In the Great Rivers of North America, much of the floodplain is isolated by an extensive levee system.   On May 3, 2011, prolonged elevated river levels near Cairo, Illinois at the confluence of the Ohio and Mississippi Rivers prompted the ACOE to demolish a large gap in the Birds Point levee above the New Madrid-St. John floodway.  The 60,000 hectare, agriculture-dominated floodplain was inundated for 1 month, during which flow, nutrient dynamics, and respiration were quantified in the floodway and in the main channel.   Nitrogen and phosphorus concentrations were similar between the river and floodway.  Once flow into the floodway stopped, chlorophyll a concentrations increased and total nitrogen declined relative to the river channel.  Dissolved oxygen in the floodway declined after separation.  The floodway was not a nitrogen source relative to the main channel.  Increased primary production following separation likely promoted the growth of river organisms, although low oxygen may have been a challenge.