Synthesis of Ecological and Physical Effects of Dam Removal Projects

Project ID: 1666
Principal Investigator: Jennifer Bountry
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2015
Keywords: dam removal, synthesis, ecology, sedimentation

Research Question

This researach effort will publish two papers that synthesize information gained in dam removal implementation projects over the last 12 years. The papers will focus on documenting questions related to reservoir sediment release:

1) How much sediment was released?
2) Where did the sediment go?
3) How long did sediment impacts last?
4) What were the common pre-removal management concerns and what actually happened?

Reserach Paper #1: Synthesis of Ecological and Physical Response to Dam Removals

Research Paper #2:
Six common engineering concerns in dam removal projects: What do 12 years of monitoring data tell us?

Need and Benefit

Dam decommissioning is rapidly emerging as an important river restoration strategy in the U.S., with several major removals recently completed or in progress. But few studies have evaluated the far-reaching consequences of these significant environmental perturbations, especially those resulting from removals
of large (>10–15 m tall) structures during the last decade. In particular, interactions between physical and ecological aspects of dam removal are poorly known. From recent work, however, observations are now available from several diverse settings nationwide to allow synthesis of key physical and ecological processes associated with dam removals, including fish and benthic community response, reservoir erosion, downstream sedimentation, water quality issues (including turbidity and contaminant transport), riparian vegetation, food web response, gene flow changes, effects on migratory aquatic species, and invasive species response. Our proposed examination and synthesis of these observations, framed and tested as hypotheses and conceptual models, will provide better understanding of the multifaceted and interrelated consequences of dam decommissioning, thereby providing a basis for formulating realistic expectations for river restoration in addition to identifying key information gaps and research needs.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Synthesis of Ecological and Physical Effects of Dam Removal Projects (final, PDF, 750KB)
By Jennifer Bountry
Publication completed on September 30, 2015

An effort to synthesize existing dam removal studies and data, thereby providing scientists and managers better knowledge of likely outcomes of future dam removals, was sponsored by the U.S. Geological Survey's John Wesley Powell Center for Analysis and Synthesis. Discussions and presentations revealed the tremendous growth of information from dam removals over the last few years, and pointed to several common patterns of physical and biological responses. For example, reservoir size and sediment characteristics, in conjunction with the type and rate of dam decommissioning, appear to lead to predictable relations between processes eroding reservoir sediment and the downstream sediment transport and channel response, which in turn affect biological conditions and trajectories. We participated in the overall synthesis of dam removal findings into a publically available database and a paper synthesizing common management concerns associated with dam removal.

The following documents were not reviewed. Statements made in these documents are those of the authors. The findings have not been verified.

Understanding the Dynamics Behind Dam Removals (final, PDF, 1.3MB)
By Jennifer Bountry
Publication completed on September 30, 2016

This bulletin summarizes the research results and potential application to Reclamation's mission.

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Last Updated: 6/22/20