The natural Upper Mississippi River (UMR) and its tributaries
flowed and meandered freely across large floodplain landscapes.
Processes such as flooding, erosion, and sedimentation were
powerful natural forces that shaped and maintained some
floodplain forest communities. Beginning in the early
nineteenth century, the UMR and its floodplain have been modified
by navigation structures and agriculture. As a consequence of
human modifications, a large portion of the UMR floodplain is no
longer periodically inundated and the hydrologic patterns in the
river, as well as on the floodplain, have changed. In general,
agriculture and urban development have greatly reduced
floodplain forest acres, especially in river reaches where a
mainline levee system has been established. Compared to
presettlement forest composition, our present floodplain forests
are generally less diverse. Silver maple has dramatically
increased in abundance and pioneer forests have probably been
greatly reduced throughout much of the UMR floodplain.
