Dams and Sediment in the Hudson (DaSH)

  • The state of New York is working to remove hundreds of dams built on tributaries of the Hudson River estuary that have outlived their usefulness. South Lattintown Creek dam; Photo credit: Andrew Meyer, NYSDEC

    The state of New York is working to remove hundreds of dams built on tributaries of the Hudson River estuary that have outlived their usefulness. South Lattintown Creek dam; Photo credit: Andrew Meyer, NYSDEC

  • When dams are removed, sediment trapped behind them will be released into the estuary.

    When dams are removed, sediment trapped behind them will be released into the estuary.

  • How will these sediments affect the estuary and its tidal marshes? The Dams and Sediment in the Hudson (DaSH) project brought scientists and stakeholders together to investigate this question.

    How will these sediments affect the estuary and its tidal marshes? The Dams and Sediment in the Hudson (DaSH) project brought scientists and stakeholders together to investigate this question.

  • The project found that the amount of sediment that could be released by dam removal is minimal compared to background sediment supply from the watershed. Crum Elbow Dam.

    The project found that the amount of sediment that could be released by dam removal is minimal compared to background sediment supply from the watershed. Crum Elbow Dam.

  • Researchers also collected data from tidal marshes, and were surprised to find that most Hudson River wetlands are remarkably young, developed unintentionally as a consequence of human activities.

    Researchers also collected data from tidal marshes, and were surprised to find that most Hudson River wetlands are remarkably young, developed unintentionally as a consequence of human activities.

  • These wetlands already have the sediment they need and are growing rapidly at a rate 2-3 times that of sea level rise.

    These wetlands already have the sediment they need and are growing rapidly at a rate 2-3 times that of sea level rise.

  • The project team and its stakeholder Advisory Committee (pictured here) used DaSH findings to develop watershed assessment tools to support dam removal permitting.

    The project team and its stakeholder Advisory Committee (pictured here) used DaSH findings to develop watershed assessment tools to support dam removal permitting.

Hundreds of dams built on tributaries of the Hudson River estuary have outlived their usefulness. Removing these relic dams is a priority for the state of New York in order to improve aquatic habitat connectivity, restore fish spawning grounds, and reduce the risk of dam failure. For those who regulate and permit dam removal, questions about the fate of sediment trapped behind these dams and its potential impact on downstream habitat has encumbered the permitting process. To better understand how sediment released by dam removal in the Lower Hudson River watershed will affect the estuary, including the potential for dam-derived sediments to help offset sea level rise in tidal wetlands, the Dams and Sediment in the Hudson (DaSH) project brought together a collaborative team of scientists and stakeholders to research key questions and provide practical tools to regulators and practitioners.

The project used a multidisciplinary approach that combined field observations with an analysis of sediment transport using a proven hydrodynamic model. A broad coalition of stakeholders from state agencies, engineering firms, and environmental restoration organizations guided research and project products to maximize their utility. DaSH answered key questions about how dam removal will impact conditions in the estuary and offered surprising new findings about tidal marshes in the Hudson River valley. Results show that most dams in the Lower Hudson River watershed are not effective sediment traps, and that dam removals would have a minimal impact on both sediment supply to the estuary and tidal wetland growth. The project developed watershed assessment tools to support dam removal permitting and established an improved scientific basis to consider potential downstream benefits in regulatory decision-making.