After the city of Wilmington removed a Brandywine dam in 2019, University of Delaware scientists discovered American shad returning to the area to reproduce. One fish the researchers tracked even made its way to Nova Scotia, Canada, and back, said assistant professor Ed Hale, who helped lead the research.

“[Dams interrupt] normal behaviors associated with animals and organismal level behaviors, but also with the flow of energy,” Hale said.  “It’s really pretty cool that the year after we remove a dam, [we] actually see that natural function.”

Flood protection

In addition to improving fish passage, scientists say dam removal is sometimes necessary to reduce the impacts of storm flooding.

Removing dams that are damaged or falling apart is the top priority, said the University of Delaware’s Gerald Kauffman, who has researched the Brandywine dams for 20 years. Unlike neighboring states, Delaware law does not require regular inspection of smaller dams, said Kauffman, who directs the university’s Water Resources Center.

One of the Brandywine River dams approved for removal is marred with a 10-by-30 foot hole. If it breaks during a major storm, an estimated 75 million gallons of water could topple downstream, Kauffman said. The researcher and professor said he’s particularly concerned about residents in northeast Wilmington — many of whom have yet to return to their homes after being flooded by Hurricane Ida in 2021.

“[Ida] was a lesson to me that we need to address [dams] now. Otherwise when the next [storm] comes down, it could be a catastrophe,” Kauffman said.

Intact dams built before the 1980s also have potential to lift already-rising water levels upstream during storms, he said, depending on a number of factors.

The dam behind Brandywine Falls appears to be in healthy condition, Kauffman said, which could mean the Army Corps of Engineers recommends stakeholders preserve it.

Brandywine Falls’ Ursomato said he would like agencies to focus on other flood-reducing infrastructure efforts instead of dam removal.

“Let’s assume you took all the dams out of the river, and the river still flooded … that would be a tragedy,” he said.

Preserving history

Brandywine Falls residents say they’re not against fish passage efforts, but are fearful they might lose a piece of Delaware history.

The dam is a remnant of Joseph Bancroft, a businessman who established a cotton mill in the area in the 19th century, taking advantage of the Brandywine’s water power.

Joseph Bancroft & Sons Co. is considered to be the most significant and longest lasting textiles company on the Lower Brandywine, according to University of Delaware historians. By the early 20th century, it became one of the world’s largest textile finishers, introducing synthetic materials to the market. Bancroft Mills is listed on the National Register of Historic Places, and may also include the dam behind Brandywine Falls.

“I feel very impassioned about the history of the area, the famous families in this area,” said Brandywine Falls  resident Jim Carrington.

Bancroft Mills is listed on the National Register of Historic Places, and the dam behind Brandywine Falls is considered a “contributing element” of the historic district. The dam is eligible for an individual listing under the registry, but hasn’t been nominated, according to the Delaware Division of Historical and Cultural Affairs.

A national register listing does not preclude a dam from removal. However, agencies involved, such as the Army Corps of Engineers are required to consult state historians and other stakeholders to determine whether the dam should be preserved due to its historical significance. If they decide a dam should remain, alternatives such as a partial removal, or a rock ramp, can be considered.

In addition to evaluating the structural condition of the dam behind Brandywine Falls, the Army Corps of Engineers will also consider its historical significance, and other fish passage options.

Hagley Museum and Library owns four dams on the Brandywine that were previously operated by the DuPonts. The famous family located their gunpowder mills along the river to take advantage of water power. The museum’s leaders have not granted permission for dam removal because they’re pursuing a historical designation for them.

“The predominant use of the powder here at Hagley was used for things like westward expansion … and so it’s a really important chapter in the history of our country,” said Jill McKenzie, the museum’s executive director.

Hagley continues to use water power to this day to keep the museum’s 1870s machine shop off the electrical grid.

The museum is partnering with the Army Corps of Engineers to determine an alternative way to improve fish passage without removing the dams, such as potentially installing a rock ladder.

David Keller, head of the fisheries section at the Academy of Natural Sciences at Drexel University, said dam removal is sometimes the most effective way to improve fish passage. However, stakeholders must also evaluate potential risks, he said.