Efforts to bolster Hudson River Estuary fisheries have focused a great deal on tributary dam removals. However, concern for sediment impacts often forestalls these projects. In the case of the Hudson, stakeholders have questioned whether sediment mobilized during dam removal might adversely affect water quality and submerged aquatic vegetation in the estuary. Others have pointed the potential benefits of releasing impounded sediment to downstream tidal marshes, which need to accumulate sediment to keep pace with sea level rise.
In close collaboration with a diverse group of stakeholders, including regulators, practitioners, and fellow scientists, our project team has quantified dam-trapped sediment inventories and characterized tidal marsh histories and sediment needs for three major tributaries of the Hudson River Estuary. Several results have help to negate common misconceptions regarding dam removals for the Hudson and likely the greater Northeast region and include: (1) sediment trapped behind unused dams comprises a very small part of the estuary’s sediment budget; (2) the majority of dams in the watershed do not trap any measurable sediment; (3) a majority of tidal marshes in the estuary are relative new to the Hudson, initiated as a result of enhanced sediment trapping by railroad causeway construction and dredge spoil impoundments. These results are contrary to widely held beliefs that may originate from other regions with different sediment transport characteristics and highlight the role of the information gap that hinders many dam removals in the Northeast.
Brian Yellen is a research assistant professor in the Department of Geosciences at the University of Massachusetts Amherst. His research focuses on watershed processes and sediment transport.
Jonathan Woodruff is an associate professor in the Department of Geosciences at the University of Massachusetts Amherst. His research centers on coastal and estuarine sedimentology.