How Tearing Down Small Dams Is Helping Restore Northeast Rivers

The glass eels, 3 inches long with skin so translucent it reveals the beating of their tiny hearts, writhe with unexpected strength in the palm of a hand. For a year they have ridden the tides from their hatching site, in the Sargasso Sea, to the mouth of upstate New York’s Saw Kill Creek, a narrow tributary of the Hudson River. That’s where a fyke net set out by biologists, counting migratory American eels as they seek clear and flowing creeks in which to mature, captures them.

Although not considered endangered by the U.S. Fish and Wildlife Service, American eels have for decades been tallied at historically low numbers throughout the Northeastern United States, the most heavily dammed region in the nation. Fishing regulators consider their stocks depleted. But they’re not the only species in trouble here. Alewife and blueback herring, shad, shortnose and Atlantic sturgeon, and Atlantic salmon are all on the decline in Northeastern river systems. In response, a range of government agencies, private landowners, and environmental groups have been collaborating to restore these populations — by removing the dams that block their passage.

Although dam removals have been happening since 1912, the vast majority have occurred since the mid-2010s, and they have picked up steam since the 2021 Bipartisan Infrastructure Law, which provided funding for such projects. To date, 806 Northeastern dams have come down, with hundreds more in the pipeline. Across the country, 2023 was a watershed year, with a total of 80 dam removals. Says Andrew Fisk, Northeast regional director of the nonprofit American Rivers, “The increasing intensity and frequency of storm events, and the dramatically reduced sizes of our migratory fish populations, are accelerating our efforts.”

After dam removal, “we see streams recover to a point where we didn’t even know there was a dam there,” says an ecologist.

Dam removals in the Northeast don’t generate the same media attention as massive takedowns on West Coast rivers, like the Klamath or the Elwha. That’s because most of these structures are comparatively miniscule, built in the 19th century to form ponds and to power grist, textile, paper, saw, and other types of mills as the region developed into an industrial powerhouse.

Subscribe to the E360 Newsletter for weekly updates delivered to your inbox. Sign Up.

But as mills became defunct, their dams remained. They may be small to humans, but to the fish that can’t get past them “they’re just as big as a Klamath River dam,” says Maddie Feaster, habitat restoration project manager for the environmental organization Riverkeeper, based in Ossining, New York. From Maryland and Pennsylvania up to Maine, there are 31,213 inventoried dams, more than 4,000 of which sit within the 13,400-square-mile Hudson River watershed alone. For generations they’ve degraded habitat and altered downstream hydrology and sediment flows, creating warm, stagnant, low-oxygen pools that trigger algal blooms and favor invasive species. The dams inhibit fish passage, too, which is why the biologists at the mouth of the Saw Kill transported their glass eels past the first of three Saw Kill dams after counting them.

Dams “cumulatively disconnect [a] river, making individually isolated environments,” says Katie Schmidt, associate director of American Rivers’ national dam removal program. The consequences for aquatic species can be enormous. “Especially as the region warms, if you’re a fish that’s trapped below a dam, there might be nice cold water a mile up that stream,” says Brian Yellen, Massachusetts’ state geologist. “But if you can’t get up it, that population is doomed.”

Left: The Saw Kill Creek dam in Red Hook, New York. Right: A glass eel found in the nearby Quassaick Creek.
Lela Nargi; Stan Honda / AFP via Getty Images

Jeremy Dietrich, an aquatic ecologist at the New York State Water Resources Institute, monitors dam sites both pre- and post-removal. Environments upstream of an intact dam, he explains, “are dominated by midges, aquatic worms, small crustaceans, organisms you typically might find in a pond.” In 2017 and 2018 assessments of recent Hudson River dam removals, some of which also included riverbank restorations to further enhance habitat for native species, he found improved water quality and more populous communities of beetles, mayflies, and caddisflies, which are “more sensitive to environmental perturbation, and thus used as bioindicators,” he says. “You have this big polarity of ecological conditions, because the barrier has severed the natural connectivity of the system. [After removal], we generally see streams recover to a point where we didn’t even know there was a dam there.”

American Rivers estimates that 85 percent of U.S. dams are unnecessary at best and pose risks to public safety at worst, should they collapse and flood downstream communities. The nonprofit has been involved with roughly 1,000 removals across the country, 38 of them since 2018. This effort was boosted by $800 million from the Bipartisan Infrastructure Law. But states will likely need to contribute more of their own funding should the Trump administration claw back unspent money, and organizations involved in dam removal are now scrambling to assess the potential impact to their work.

Low-head dams, over which water flows continuously, churn up currents that trap and drown 50 people a year in the U.S.

Enthusiasm for such projects is on the upswing among some dam owners — whether states, municipalities, or private landholders. Pennsylvania alone has taken out more than 390 dams since 1912 — 107 of them between 2015 and 2023 — none higher than 16 feet high. “Individual property owners [say] I own a dam, and my insurance company is telling me I have a liability,” says Fisk. Dams in disrepair may release toxic sediments that potentially threaten both human health and wildlife, and low-head dams, over which water flows continuously, churn up recirculating currents that trap and drown 50 people a year in the U.S.

In a major reversal, the World Bank is backing mega dams. Read more.

Numerous studies show that dam removals improve aquatic fish passage, water quality, watershed resilience, and habitat for organisms up the food chain, from insects to otters and eagles. But removals aren’t straightforward. Federal grants, from the National Oceanic and Atmospheric Administration or the Fish and Wildlife Service, favor projects that benefit federally listed species and many river miles. But even the smallest, simplest projects range in cost from $100,000 to $3 million. To qualify for a grant, be it federal or state, an application “has to score well,” says Scott Cuppett, who leads the watershed team at the New York State Department of Environmental Conservation’s Hudson River Estuary Program, which collaborates with nonprofits like Riverkeeper to connect dam owners to technical assistance and money. The application is daunting and can require proof that a removal will conserve or restore migratory fish habitat and reduce flood impacts, sediment and feasibility assessments, plans for accompanying riparian plantings, permits, designs, and letters of support from legislators and neighbors.

All this can be overwhelming for dam owners, which is why stakeholders hope additional research will help loosen up some of the requirements. In 2020, Yellen released a study in which he simulated the removal of the 1,702 dams in the lower Hudson watershed, attempting to determine how much sediment might be released if they came down. He found that “the vast majority of dams don’t really trap much sediment,” he says. That’s good news, since it means sediment released into the Hudson will neither permanently worsen water quality nor build up in places that would smother or otherwise harm underwater vegetation. And it shows that “you would not need to invest a huge amount of time or effort into a [costly] sediment management plan,” Yellen says. It’s “a day’s worth of excavator work to remove some concrete and rock, instead of months of trucking away sand and fill.”

However, studies on the impacts of sediment quality are still lacking. Sediment trapped behind the dam of a felting mill, which processed wool, might contain mercury, for example, which could cause a state’s environmental agency to nix removal plans — even if that contaminated sediment is, says Yellen, “cleaner than what’s already downstream.”

On Quassaick Creek, where a dam came out in 2020, American eel and juvenile blue crabs have already moved in.

On a sunny winter afternoon, Feaster, of Riverkeeper, stands in thick mud beside Quassaick Creek in Newburgh, New York. The Strooks Felt Dam, the first of seven municipally owned dams on the lower reaches of this 18-mile tributary, was demolished with state money in 2020. The second dam, called Holden, is slated to come down in late 2025. Feaster is showing a visitor the third, the Walsh Road Dam, whose removal has yet to be funded. “This was built into a floodplain,” she says, “and when it rains the dam overflows to flood a housing complex just around a bend in the creek.”

Community support for removal of the first three dams was high. But removing the fourth dam, at Muchattoes Lake, might prove trickier. At 23 feet high, it’s a significant impediment to eel passage. But its impoundment provides the one nearby place townspeople can kayak and fish, which means Feaster’s team will have its work cut out to convince them of the benefits of removal.

There are also ecological reasons to leave dams intact. If pike, an introduced, aggressive sport fish, “gets up into the headwaters” of the Penobscot River, in Maine, where the removal of two dams in 2012 and 2013 reopened 2,000 miles to 12 sea-run fish species, Fisk says, “it would be very happy to snack on all those native wild brook trout.” The solution in some of these instances: Leave the dam in place and install a fish ladder that sorts out pike and other invasives like rock bass and channel catfish.

Quassaick Creek flows freely after the removal of the Strooks Felt Dam, Newburgh, New York.
Jessie Deitz

On the Quassaick, improvements are evident since the Strooks dam came out. American eel and juvenile blue crabs have already moved in. In fact, fish returns can sometimes be observed within minutes of opening a passageway. Says Schmidt, “We’ve had dammed rivers where you’ve been removing the project and when the last piece comes out a fish immediately storms past it.”

Invasive knotweed lines the creek bank near the Walsh Road dam, but above a nearby culvert, Riverkeeper and New York State’s Trees for Tribs initiative recently planted 105 young willows and other native trees. Similar plantings will replace the knotweed after the dam comes down, to prevent erosion and to provide shade to cool the creek and falling leaves to oxygenate it. “It’s really important when we’re removing barriers to make sure that the whole area is restored,” says Catherine Bozek, national fish passage program coordinator for Fish and Wildlife Service’s Northeast region. Riparian areas often revegetate themselves, she says, “but we want to make sure that we’re managing any invasive species that may come in” to ensure better stream health and provide habitat and food for local organisms.

As drought shrivels hydro, this African nation pivots to solar. Read more.

There is palpable impatience among environmentalists and dam owners to get even more removals going in the Northeast. To that end, collaborators are working to streamline the process. The Fish and Wildlife Service, for example, has formed an interagency fish passage task force with other federal agencies, including NOAA and FEMA, that have their own interests in dam removals. American Rivers is working with regional partners to develop priority lists of dams whose removals would provide the greatest environmental and safety benefits and open up the most river miles to the most important species. “We’re not going to remove all dams,” says Schmidt. “But we can be really thoughtful and impactful with the ones that we do choose to remove.”

O post How Tearing Down Small Dams Is Helping Restore Northeast Rivers apareceu primeiro em EcoNewsOnline.