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Dam Removal

Dams in the Hudson WatershedBy identifying and supporting the removal of dams that are at risk of failure and are barriers to fish passage, the Hudson River Estuary Program and its partners promote ecosystem functioning and habitat connectivity while reducing threats to human safety and property.

 

Many dams in the Eastern U.S. are falling into disrepair and no longer serve their original purpose, yet still create barriers to fish passage. With over 1,600 inventoried dams in the Hudson River Estuary Watershed and likely just as many smaller, undocumented ones, there is a great opportunity to improve the ecosystem, and reduce and eliminate localized and downstream flood risks by identifying and removing those barriers that pose the greatest risks to both.

Barrier removal success story

Alewives in the Wynants Kill
Alewives in the Wynants Kill

Habitat for migratory fish, such as herring and American eel, as well as many other aquatic species (e.g., Brook Trout) has been substantially reduced by barriers in Hudson River tributaries. In the City of Troy, the first upstream barrier to fish was removed on the Wynants Kill in early May of 2016, and in less than 5 days, alewives had retaken the tributary as spawning habitat for the first time in 85 years. The City of Troy received a tributary restoration grant from the NYSDEC Hudson River Estuary Program and removed the barrier, reconnecting over a quarter mile of spawning habitat for herring, and improving habitat for many other species including American eel. A partnership between New York State Water Resources Institute (NY WRI), NYSDEC, and Riverkeeper led to the removal of this critical barrier and was an immediate success.  Watch videos of the herring run here Alewives in the Wynants Kill and Alewives and the concrete channel of the Wynants Kill.

Research

Maiden Lane Dam on the Furnace Brook
Dams like this one on the Furnace Brook in Westchester County not only block upstream habitat for migratory fish but are potential hazards for flooding and liability.

The New York State Water Resources Institute and the Hudson River Estuary Program have supported studies to inform local decision making around the potential pros and cons of dam removal.

  • Weiming Wu of Clarkson University characterized the volume of erodible sediments and their contaminant concentration behind the Bingham Mills Dam on Roeliff Jansen Kill and Burden Pond Dam on Wynants Kill Creek.
  • Cornell’s Department of Natural Resources continues to monitor chemical, biological, and physical conditions at a number of dam sites in the Hudson Valley, such as Furnace Brook (Westchester County), Otter Kill (Orange County), Quassaick Creek (Orange County), Poesten Kill (Rensellear County), and East Branch of Wappinger (Dutchess County) to allow researchers and managers to understand the ecological success of these removal projects.  Read more about this project at "Hudson Tributary Dam Removal."
  • At a broader scale, Christina Tonitto and Susan Riha of Cornell University conducted a review of dams removed in the last two decades throughout the United States, and summarized the lessons learned from these cases into six recommendations: engage stakeholders, streamline planning through policy changes, monitor pre- and post-dam removal, expect aquatic organism population recovery to vary, expect chemical changes to vary, and prioritize predicting post-removal hydrologic flows, using a program such as HEC-RAS. For More details, see their paper in Sustainable Water Resource Management.

In addition to these completed and ongoing research and monitoring projects, a broader research agenda is emerging to:

  1. Better understand the social dimensions and policy barriers to dam removal,
  2. Develop tools with, and for, local habitat restoration managers and outreach practitioners to more effectively implement projects, and
  3. Identify the smaller undocumented (“ghost”) dams/barriers through aerial imagery and machine learning.

Click here to learn more.