Two dams in southern Wisconsin over 100 years old were breached in summer 2000 as a step before complete removal later that year. Geomorphic and biogeochemical data were collected prior to breaching. Both impoundments were trapping suspended and bedload sediments prior to drawdown. Suspended-sediment loads downstream increased dramatically following dam breaching while bedload remained unchanged. Based on data for dam removals in other physiographic regions, as well as geomorphic analogies from disturbed fluvial systems, we propose a conceptual model for channel recovery following dam removal.
Channel systems can follow one of three pathways toward equilibrium following dam removal.
Recognition of these different response styles and timescales has important implications for removal techniques and for developing policies related to dam removal. Doyle, M.W., E.H. Stanley, T.S. Hooyer, and J.M. Harbor. Preliminary Results from Two Case Studies. More than 300 dams have been removed in the past 50 years, and many more are scheduled to be removed. Dam removal provides excellent opportunities for large-scale environmental river restoration as well as unique opportunities for the study of geomorphic and ecological system responses to significant disturbance.