Abstract
In recent years, environmental groups and government agencies have begun to reassess the value of dams present on numerous rivers throughout North America. Increasingly this assessment has led to the removal of dams, particularly those that have outlived their original purpose, present significant safety concerns, or have environmental impacts that are now considered unacceptable. The idea of removing dams is a controversial one and can have significant political, economic, and environmental repercussions. The apparent success of some dam removals has resulted in calls for much larger dams, such as those found on the Elwha and Snake Rivers in Washington State, to be removed as a strategy to help restore runs of endangered anadromous fish. The reported benefits of dam removal, however, are not well documented in the scientific literature. Most dam removals have been accomplished only recently, and usually without formal ‘before’ and ‘after’ removal monitoring. Only three articles in the scientific literature investigate the effects of dam removal with reference to actual case studies (Hill et al., 1994; Shuman, 1995; Kanehl & Lyons, 1997). More information about dam removal effects can also be found in gray literature, such as departmental reports, but important information can easily be missed because much of this is difficult to find and access.
This paper attempts to draw together information from scientific journals, as well as gray literature sources such as internal reports, official websites, and environmental professionals, to obtain a detailed understanding of the environmental consequences associated with dam removal.