Abutment – That part of the valley side against which the dam is constructed. An artificial abutment is sometimes constructed, as a concrete gravity section, to take the thrust of an arch dam where there is no suitable natural abutment. The left and right abutments of dams are defined with the observer viewing the dam looking in the downstream direction, unless otherwise indicated. (Source: Federal Energy Regulatory Commission (FERC)

Alluvial – Sediment deposited by flowing water, such as in a riverbed. (Source: U.S. Society on Dams)

Amphidromous – Migrating from fresh to salt water or migrating from salt water to fresh water at some stage of the life cycle other than the breeding or spawning period. (Source: U.S. Fish & Wildlife Service)

Anadromous – Fish that live in salt water as adults and spawn in fresh water. (Source: U.S. Fish & Wildlife Service)

Breach – An opening through a dam that allows the uncontrolled draining of a reservoir. A controlled breach is a constructed opening. An uncontrolled breach is an unintentional opening caused by discharge from the reservoir. A breach is generally associated with the partial or total failure of the dam. (Source: FERC)

Catadromous – Fish that live in fresh water as adults and spawn in salt water. (Source: U.S. Fish & Wildlife Service)

Crest – A line running between abutments describing the upper limit of a dam. (Source: The United States Society on Dams)

Dam Failure – Catastrophic type of failure characterized by the sudden, rapid, and uncontrolled release of impounded water or the likelihood of such an uncontrolled release It is recognized that there are lesser degrees of failure and that any malfunction or abnormality outside the design assumptions and parameters that adversely affect a dam’s primary function of impounding water is properly considered a failure. These lesser degrees of failure can progressively lead to or heighten the risk of a catastrophic failure. They are, however, normally amenable to corrective action. (source: Association of State Dam Safety Officials)

Dam safety – Dam safety is the art and science of ensuring the integrity and viability of dams such that they do not present unacceptable risks to the public, property, and the environment. It requires the collective application of engineering principles and experience, and a philosophy of risk management that recognizes that a dam is a structure whose safe function is not explicitly determined by its original design and construction. It also includes all actions taken to identify or predict deficiencies and consequences related to failure, and to document, publicize, and reduce, eliminate, or remediate to the extent reasonably possible, any unacceptable risks. (FERC)

Fishway/Fish ladder – An apparatus that lets fish swim around a dam or a waterfall. (Source: U.S. Fish & Wildlife Service)

Spillway – A structure over or through which flow is discharged from a reservoir. If the rate of flow is controlled by mechanical means, such as gates, it is considered a controlled spillway. If the geometry of the spillway is the only control, it is considered an uncontrolled spillway. (source: Association of State Dam Safety Officials) 

Tailwater – The water immediately downstream from a dam. The water surface elevation varies due to fluctuations in the outflow from the structures of a dam and due to downstream influences of other dams or structures.  Tailwater monitoring is an important consideration because a failure of a dam will cause a rapid rise in the level of the tailwater. (Source: FERC)



This summer, Laura Wildman presented a webinar on the most common mistakes in dam removal.

On June 21-24 2021, the World Fish Migration Foundation hosted the annual Fish Passage conference. The conference included a presentation by Brian Cluer on adding dimension to fish passage projects by applying Stage 0 restoration approach.


America’s Most Endangered Rivers® reports (produced by American Rivers)

American Rivers

Dam Removal Europe

Elwha River Restoration (National Park Service)

International Rivers

Lower Elwha Klallam Tribe

NOAA Northwest Fisheries Science Center

Rewilding Europe has launched a dam removal network

The Conservation Fund – Removal of Lower Eklutna River Dam

The Nature Conservancy

World Fish Migration Foundation

World Wildlife Fund – Free Flowing Rivers


American Rivers. America’s Most Endangered Rivers® reports

American Rivers. Map of U.S. Dams removed since 1912 

American Society of Civil Engineers 2021 Report Card for America’s Infrastructure,

Aspen Institute. 2002. Dam Removal: A New Option for a New Century. The Aspen Institute, Washington, DC. 68 pp.

Babbitt, B. 2002. “What goes up, may come down”. Bioscience 52(8): 656-58.

Bednarek, A.T. 2002. “Dams and Decision-making: Balancing socioeconomic and ecological considerations”. Ph.D. dissertation. University of Pennsylvania, Philadelphia, PA.

Bednarek, A.T. 2001. “Undamming rivers: a review of the ecological impacts of dam removal”. Environmental Management 27: 803-14.

Bowman, M.R. 2002. “Legal perspectives on dam removal”. Bioscience 52(8): 739-47.

Centro Ibérico de Restauración Fluvial (CIREF) and Wetlands International European Association, 2017. Criteria for decision-making towards the improvement of river connectivity and dam removal considering the impacts of invasive fish species in the Iberian Peninsula.

Cui, Yantao & Booth, Derek & Monschke, Joel & Gentzler, Seth & Rodifer, John & Greimann, Blair & Cluer, Brian. (2016). Analyses of the Erosion of Fine Sediment Deposit for a Large Dam Removal Project: an Empirical Approach. International Journal of River Basin Management. 15. 1-44. 10.1080/15715124.2016.1247362.

Cluer, Brian & Thorne, Colin. (2014). A Stream Evolution Model Integrating Habitat and Ecosystem Benefits. River Research and Applications. 30. 10.1002/rra.2631.

De Graff, Jerome & Evans, James. (2013). The Challenges of Dam Removal and River Restoration Reviews in Engineering Geology Volume 21. 10.1130/REG21. The Challenges of Dam Removal and River Restoration

  • Laura Wildman, 2013. “Dam removal: A history of decision points”, The Challenges of Dam Removal and River Restoration, Jerome V. De Graff, James E. Evans

Grill, Günther & Lehner, B. & Thieme, Michele & Geenen, B. & Tickner, David & Antonelli, Francesca & Babu, S. & Borrelli, Pasquale & Cheng, L. & Crochetiere, H. & Ehalt Macedo, Heloisa & Filgueiras, R. & Goichot, Marc & Higgins, Jonathan & Hogan, Zeb & Lip, B. & McClain, Michael & Meng, J. & Mulligan, Mark & Zarfl, Christiane. (2019). “Mapping the world’s free-flowing rivers. “Nature. 569. 215-221. 10.1038/s41586-019-1111-9.

E. Richard Hart, Endangered Rivers and the Conservation Movement. By Tim Palmer, Environmental History Review, Volume 11, Issue 3, Fall 1987, Pages 234–235,

River Alliance of Wisconsin and Trout Unlimited. 2017 Dam Removal – A Citizens Guide to Saving Rivers (2017).

A Broad level classification system for dam removals (2011). Wildman, L. & Macbroom, J.

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