Human Alterations of Rivers

Abstract

People have been altering the environment since prehistory. Archeological records and the stratigraphy of valley bottoms suggest that prehistoric alteration of native upland vegetation for grazing and crops resulted in enhanced sediment yields to river corridors, as well as associated changes in channel dimensions and planform and channel-floodplain connectivity (e.g., Mei-e and Xianmo 1994; Stinchcomb et al. 2011). The magnitude of these changes varied through time and space. Examples of intensive vegetation clearing and valley-bottom aggradation come from diverse regions. In the southeastern United States, nineteenth century row-crop agriculture led to floodplain deposition of more than a meter of sediment (Jackson et al. 2005). In southeastern Australia, nineteenth century land clearance caused channel and floodplain aggradation (Brooks and Brierley 1997). In southern Poland, land clearance for agriculture during the late seventeenth to nineteenth centuries triggered increased sediment yields that changed meandering rivers into braided channels (Latocha and Migoń 2006). Conversely, twentieth century declining resource use, regrowth of upland vegetation, and erosion of channels occurred in mountainous regions of western and central Europe (Latocha and Migoń 2006).