The Gulf Coastal Plains and Ozarks (GCPO) region is, to a large extent, defined by its mainstem big rivers, with eight of the largest ten rivers (by discharge) in the lower U.S. terminating here. Those rivers are the Mississippi, Ohio, Missouri, Tennessee, Mobile, Atchafalaya, Red, and Arkansas. While
this assessment focuses on rivers of the MAV, the analysis has also been extended to big rivers throughout the GCPO.
People have historically altered large river systems through the construction of levees and floodways, channelization, and dredging to support agriculture, navigation, commerce, and to provide greater stability and protection from flooding. Many large rivers in the GCPO are, in fact, part of the
inland commercial navigation network. Channel alterations have however impacted the ecological function of big rivers of the GCPO. One of the goals of this assessment is to define a suite of key characteristics that are important to good ecological functioning of large river systems and then
identify locations where this suite of characteristics may be found in the GCPO.
To capture floodplain dynamics, this Assessment relies heavily on the GCPO’s inundation frequency dataset (IF). The IF has been demonstrated to accurately characterize floodplain inundation under a variety of typical seasonal flooding scenarios. In addition, this Assessment uses a new analysis
based on the IF to quantify the degree of lateral connectivity between the mainstem and the adjacent floodplain This new analysis may reveal important characteristics regarding not only floodplain extent , but also function, and thermal characteristics at the landscape scale. These two datasets
represent a huge improvement in understanding large river function in the GCPO, where these systems dominate the landscape.
