Abstract
Distinguishing human impacts on channel morphology from the natural behaviour of fluvial systems is problematic for large river basins. Large river basins, by virtue of their size, typically encompass wide ranges of geology and landforms resulting in diverse controls on channel form. They also inevitably incorporate long and complex histories of overlapping human and natural disturbances. Wide valleys were historically prime locations for human settlement, as immigrants were attracted to relatively flat and fertile flood-plain soils, and rivers served as conduits of travel and commerce. Over the span of multiple centuries, humans typically modified many aspects of a river's hydraulic and hydrologic behaviour, including streamflow regimes, bank erodibility, and sediment supply. Distinguishing anthropogenic impacts from natural influences in large river basins is therefore difficult because there are so many potential drivers of channel change, and human interventions have occurred over long timescales.
Citation
Wallick, Jennifer Rose; Grant, Gordon E.; Lancaster, Stephen T.; Bolte, John P.; Denlinger, Roger P. 2007. Patterns and controls on historical channel change in the Willamette River, Oregon, USA. In: Gupta, A. ed. Large rivers: geomorphology and management. John Wiley & Sons: 491-516. Ch. 23.
