New Publication: Sediment Supply and Potential Impacts of Dam Removals

Thursday, February 11, 2021
Sediment Trap

All 1700 dams were placed into categories. More than half of the impoundments were “non-sources” of sediment – meaning dam removal would not substantially alter downstream sediment conditions.

A new study by a team including NE CASC researchers Brian Yellen and Jon Woodruff reveals that man-made dams built in the Lower Hudson watershed do not trap as much sediment from riverways as previously believed. These findings are particularly important for the many Hudson River communities seeking to remove existing man-made dams that are no longer needed for industrial use and may negatively impact wetlands or interfere with local river restoration efforts.

Over the past several years, more than 600 man-made dams have been removed from New York, New Jersey and New England, a trend that is accelerating. Nevertheless, this subject remains contentious due to concerns that dam removal will release large amounts of previously trapped sediment and overwhelm downstream river ecosystems. According to Yellen and Woodruff, the more than 1,700 dams they evaluated in the Lower Hudson watershed trapped only four years’ worth of sediment—even though the dams under consideration have typically existed for more than one hundred years.

“Dams make it hard for fish and other animals that live in rivers to move around,” said Yellen. “Communities want to remove old dams, but some individuals are worried that the mud behind the dams will get washed downstream and hurt fish and turtles and plants. But our studies show that there’s actually not that much mud stuck behind those structures. Hopefully our results will help these communities and their decision-makers continue their efforts to remove dams and restore rivers.”

The researchers also created a public-facing tool to help dam owners and engineers overseeing dam removals quickly estimate the amount of sediment trapped behind dams.

The article, “Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary,” appears in the January edition of Estuaries and Coasts.

This work was recently featured on the UMass Amherst website. Click here to read the full press release. 

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