The Mississippi River Floodplain: Current Status and Historical Perspective

Waters of the Mississippi River historically inundated vast areas of floodplain during the spring flood pulse and provided a mechanism of lateral exchange of energy and nutrients between the aquatic and terrestrial habitats.  During a typical year Mississippi River water levels are highest in the spring and lowest in the fall, but levels can vary year to year.  Many species of fish have adapted feeding and reproductive strategies to take advantage of the predictable change in water level, and may be negatively impacted when the timing or duration of the flood pulse is altered.  As human populations increased on the Mississippi River floodplain, construction of flood-protection levees and navigational structures severely decreased the connectivity between the river and floodplain.  Construction of flood protection levees has reduced the size of the Mississippi River floodplain by over 90%.  Fluvial dynamics, the driving force in maintaining diverse floodplain habitat, has been altered along 80% of the River’s length. Although much of the historic floodplain has been isolated and converted to agricultural land with significant economic value, there are many projects along the Mississippi River that are reconnecting the river to a portion of its historic floodplain to restore river-floodplain ecological structure and function.