New Report Synthesizes U.S. Dam-Removal Studies

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The rate of dam removal in the U.S. has increased over past decades, motivating a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review available dam-removal studies. The synthesis of their findings, “Dam removal: Listening in,” appeared July 31 in the American Geophysical Union (AGU) journal Water Resources Research. The abstract is given here.

This article is part of the August-October 2017 issue of the Sound Waves newsletter

View of Glines Canyon Dam before removal

View of Glines Canyon Dam before removal. Photo credit: USGS

View of Glines Canyon Dam 2.5 weeks after removal began

View of Glines Canyon Dam 2.5 weeks after removal began. Photo credit: USGS

Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad-scale ecological effects, and gives managers information needed to understand and predict long-term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam-removal methods in the U.S.

The full citation for the article is:

Foley, M.M., Bellmore, J., O’Connor, J.E., Duda, J., East, A., Grant, G.G., Anderson, C., Bountry, J.A., Collins, M.J., Connolly, P.J., Craig, L.S., Evans, J.E., Greene, S., Magilligan, F.J., et al., 2017, Dam removal—Listening in: Water Resources Research, doi: 10.1002/2017WR020457.