11 dams removed in Delaware River Basin to benefit wildlife

Eleven dams in the Delaware River Basin were removed last year, in a move that environmental advocacy groups say will improve conditions for wildlife in the Delaware’s tributaries and remove hazards for nearby communities.

The nonprofit American Rivers connects annually with its national partners to catalogue the removal of obsolete man-made dams. Its 2024 report said no state removed more dams than Pennsylvania, where a total of 27 dams were cleared from various rivers and creeks.

“I like to compare a dam in a river to a blood clot in an artery of your body,” said Jessie Thomas-Blate, director of river restoration at American Rivers. “You want your blood to be able to flow freely and not be obstructed, and the same thing is true with rivers and the water and nutrients that flow through them.”

Read more: The beneficiaries of removing mill dams in Delaware River watershed? ‘Fish, fish, fish’

Dam removals can open up spawning grounds for migratory fish species in the region like the American shad, Alewife and Blueback herring, Thomas-Blate said. 

The increased water flow after a dam is removed can also benefit an ecosystem by helping to regulate temperatures and oxygen levels in a body of water.

“If you have an impoundment where [a body of water] is not moving, then the oxygen starts to get depleted by fish and algae consuming it, so oxygen levels go down,” Thomas-Blate said. “And if the water isn’t moving, it’s more susceptible to be heated up by the sun, and you might also have cooler water moving from headwaters down through the system if a dam wasn’t there.”

Nine of the dams removed were in Pennsylvania and the other two were in New Jersey. They were: the Cedar Grove and Paulina Dams in New Jersey; and the Archibald Johnston Conservation Area Dams 1 through 6, the City of Easton Lower, Dilldown Creek and Lorimer Reserve Upper Pond Dams.

Risks to humans

An estimated 14,000 obsolete dams in the Northeast can also pose risks to people.

“There are a lot of injuries that can happen around dams,” said Chris Arnott, freshwater project manager for the Nature Conservancy in Pennsylvania. “The liability of owning a dam can be pretty high, between people getting hurt and the potential for the dam to fail and cause flooding downstream.”

The New Jersey chapter of the Nature Conservancy was a partner in the removal of the Paulina Dam on the Paulins Kill River, one of the dam removals that took place in the Delaware River Basin in 2024.

Read more: Dam removal leads to rebirth of the Paulins Kill

The obsolete dams in the Delaware River Basin used to have a range of functions, from recreational purposes to use at old mills.

“The normal design life for a dam is typically around 50 years, so when you’re looking at Pennsylvania, which has a huge number of dams and a huge number of 100-plus-year-old dams, that creates a large liability,” Arnott said.

Six of the Delaware River Basin’s dam removals in 2024 took place at Monocacy Creek in Northampton County, Pa. Monocacy Creek is a tributary of the Lehigh River, which itself is a tributary of the Delaware. Northampton County partnered with the nonprofit Wildlands Conservancy for the project.

“The site was originally owned by the president of the steelworks in Bethlehem, who later became the first mayor of the city,” said Kristie Fach, director of ecological conservation at the Wildlands Conservancy. “This was his recreation area and the stream had been manipulated with channelization, rock walls on either side, and a series of dams to direct the stream into a circle for paddle boats.”

In the roughly 100 years since the recreation area was built, the dams and other structures had fallen into a state of disrepair. Several bridges that once crossed over the creek had collapsed and were creating their own obstacles for water and wildlife. The waters upstream of the former recreation spot are home to trout, so the removal of the dams and other blockages in the area restored a connection to the Monocacy for trout populations. 

Read more: Man-made lakes, loved by humans, can harm the environment

More dam removals planned

Thomas-Blate said American Rivers is happy to see projects that address the health of a body of water holistically, removing a sequence of dams in an area, like the initiative at Monocacy Creek.

The Wildlands Conservancy plans to continue to remove obsolete dams in the Delaware River Basin. It plans dam removals at Bushkill Creek, another tributary of the Lehigh River, where it has done some work in the past.

“We’re really systematic on removing the next dam upstream,” Fach said. “We’ve removed five on the Bushkill to date and we have another plan for next year and then hopefully more in the future.”

The Nature Conservancy also continues to prioritize removing dams in the Delaware River Basin. In 2022, it published a restoration road map to guide future projects to improve aquatic connectivity and habitat quality for migratory fish populations in the Delaware and its tributaries.