Prairie Landscape Change and Flooding in the Mississippi River Valley

Extensive landscape alteration of prairie in the U.S. from agricultural expansion has reduced waterfowl populations and increased precipitation runoff into regional river basins. Satellite imagery shows that prairie landscapes have been less altered in Canada than in the U.S. Long-term, broad-scale precipitation data indicate that in both countries precipitation has varied widely but has not increased over time. Nevertheless, flow rates of unregulated U.S. rivers have increased, but there have been no detectable changes in flow rates of Canadian rivers. Neither of two competing hypotheses advanced to explain increasing flood magnitudes—climate change and channel confinement—can account for these results. Thus, the increased magnitudes of floods in the Mississippi River Valley over the last several decades may be at least partially related to extensive changes in agricultural land use resulting in reduction of natural upland vegetation and wetland drainage in the upper reaches of this watershed.