Geology topics

Research about Upper Mississippi River Floodplain

Source-linked reports with geographic coverage including Upper Mississippi River Floodplain.

2 recordsLinked to original sources

USGS2012

Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA

Most large rivers have experienced major changes in hydrology and land use over the past century, with concomitant effects on sedimentation, nutrient cycling and biodiversity. To restore and/or enhance these ecosystems, managers need to know where their efforts are most likely to succeed under current hydrologic regimes as well as under potential future hydrologic regimes. We therefore examined changes in forest vegetation and soils across a hydrologic gradient, expressed as flood duration during the growing season, for 320 km of the Upper Mississippi River (UMR) floodplain. Soil texture was highly variable but trended toward finer grained sediments and >5% organic matter as flood duration increased from 0% to ~40% of the growing season. Beyond 40%, soil texture was exclusively silt plus clay with >5% organic matter. The diversity of both the understory and overstory tree communities was also highly variable at sites that flooded for <40% of the growing season. However, understory diversity decreased as flood duration increased from 0% to ~25% of the growing season and overstory diversity declined as flood duration increased from 0% to ~40% of the growing season. Diversity estimates for both strata were uniformly low at sites that flooded for longer than ~40% of the growing season. Beyond this point the proportional abundance of Acer saccharinum in the overstory exceeded 70%. Our results suggest that there is a threshold along the elevation gradient of this floodplain, corresponding with flood durations lasting ~40% of the growing season. At lower elevation sites, flooding exerts primary control over forest soils and vegetation, restricting the former to silt plus clay with higher organic matter and the latter to a few highly flood tolerant species. The existence of such thresholds have implications for management of floodplain soil nutrient dynamics and plant diversity under existing hydrologic regimes, more natural hydrologic regimes and more extreme hydrologic regimes that may result from climate change.

Iowa;Minnesota;Wisconsin↗

USGS2011

Past and predicted future changes in the land cover of the Upper Mississippi River floodplain, USA

This study provides one historical and two alternative future contexts for evaluating land cover modifications within the Upper Mississippi River (UMR) floodplain. Given previously documented changes in land use, river engineering, restoration efforts and hydro-climatic changes within the UMR basin and floodplain, we wanted to know which of these changes are the most important determinants of current and projected future floodplain land cover. We used Geographic Information System data covering approximately 37% of the UMR floodplain (3232 km 2 ) for ca 1890 (pre-lock and dam) and three contemporary periods (1975, 1989 and 2000) across which river restoration actions have increased and hydro-climatic changes have occurred. We further developed two 50-year future scenarios from the spatially dependent land cover transitions that occurred from 1975 to 1989 (scenario A) and from 1989 to 2000 (scenario B) using Markov models.Land cover composition of the UMR did not change significantly from 1975 to 2000, indicating that current land cover continues to reflect historical modifications that support agricultural production and commercial navigation despite some floodplain restoration efforts and variation in river discharge. Projected future land cover composition based on scenario A was not significantly different from the land cover for 1975, 1989 or 2000 but was different from the land cover of scenario B, which was also different from all other periods. Scenario B forecasts transition of some forest and marsh habitat to open water by the year 2050 for some portions of the northern river and projects that some agricultural lands will transition to open water in the southern portion of the river. Future floodplain management and restoration planning efforts in the UMR should consider the potential consequences of continued shifts in hydro-climatic conditions that may occur as a result of climate change and the potential effects on floodplain land cover.

Illinois;Iowa;Minnesota;Missouri;Wisconsin↗