Historical sources and watershed evolution.

Historical data, including structures, documents, photographs and eyewitness reports, allow changes in some drainage basins to be documented in fine detail over time periods ranging from a few days to several decades. The USA is rich in data sources that are freely available. Rates of bank erosion, meander migration, channel width, riparian vegetation and watershed land use and cover conditions can be assessed, which are especially valuable where there is controversy over the human contribution to erosion and deposition. Studies of Coon Creek and the southern Piedmont of the USA have yielded results that sometimes contradict established views.