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Alewives returning by the millions after the removal of the Edwards and Ft. Halifax dams were removed from the Kennebec River of Maine.

Dam Removal Successes

By Jason Kahn 

Featured Image: Alewives returning by the millions after the removal of the Edwards and Ft. Halifax dams were removed from the Kennebec River of Maine. (Photo by John Burrows/ASF)

Amongst the most threatened of global habitats are freshwater ecosystems.  With water pollution from our industrial past and farm runoff that continues today, rivers and streams have taken a big hit.  The clean water act passed in the ‘70’s has helped return health to some rivers and streams allowing freshwater fish to return in good numbers to their former haunts.  Anadromous fish (those that are born in freshwater, spend most of their lives in saltwater and return to their freshwater streams to spawn) are the keystone species of healthy freshwater ecosystems.

However, the hundreds of thousands of dams in the U.S. that restrict the passage of these fish from reaching their traditional headwaters have not allowed full health to be restored in these vital ecosystems.  For centuries now keystone species in the eastern waterways such as American shad, hickory shad, American eel, and striped bass have been stymied in their journeys upstream to spawn.  The resulting collapse of their populations has been attributed to dams and overfishing in the resulting pools below dams.

The tide as luck would have it is turning.  Here in the United States, federal and state agencies, along with a diverse collective of conservation groups ranging from American Rivers to sportfishing groups, have been removing dams at a rate that borders on frantic.  In the past 20 years, 1,268 dams have been removed from America’s rivers and streams.  Some of these are large licensed facilities such as the Elwha Dam on Washington’s Elwha River in 2012.  Most, however, are centuries-old mill and farm dams that were built before such construction required a license.  States such as California and Pennsylvania are leading the way in the rewilding of America’s rivers and streams.  The move to return anadromous fish to their traditional spawning waterways is fueling a rapid return of fish in months rather than years as was predicted.

Aquaculture and fisheries specialists pull a seine net through the Brandywine Creek monitoring shad migration.

Aquaculture and fisheries specialists pull a seine net through the Brandywine Creek monitoring shad migration. (Credit: University of Delaware)

Brandywine Creek, a tributary of the Delaware River, America’s largest undammed river in the east, enters the Christina River less than a mile before it enters the Delaware River in the city of Wilmington on the edge of Delaware Bay.  The Brandywine had its first dam removed in the fall of 2019.  The West Street Dam was the first of 11 dams planned for removal or modification on the Brandywine, and the spring and summer of 2020 saw American and hickory shad swim past the remnants of the dam 0.8 miles upstream to the base of the next dam.  This dam and the next upstream dam are slated for removal in the near future.  The plan is to remove or modify the existing dams with fish ladders.  These ladders are a series of short steps that go up to the crest of a dam and allow these important species, indicators of freshwater health, to travel up into the streams of Pennsylvania 25 miles upstream.  With the upstream advance of the shad, eel, and bass other keystone species of freshwater health such as the bald eagle and the osprey have followed.  Hitching a ride in the gills of the migrating fish are freshwater mussels so important for filtering pollution from river sediments. These bottom-dwelling filter feeders clean the water and sediment of toxins. These toxins, however, may render them inedible to humans or predatory birds if the concentration of toxins is too high.

So transformed was the Brandywine that anglers in April of 2020 caught unheard of numbers of shad in the newly opened section of the creek.  Where the fish go the birds will follow.  If riparian habitats are restored to a healthy state trees and cover will need to be allowed to return to the rivers’ edges to prevent erosion from silting up streams and allow habitat for the newly returned eagle and osprey.  These greenways around and through America’s cities are important wildlife corridors.  Shy species such as fox and bobcat use these ribbons of green space to connect forest habitats miles apart.

These restored freshwater habitats also increase humans’ enjoyment of the waterways such as kayaking or birdwatching.  During the pandemic many urban and suburban citizens have flocked to these bits of green space as a refuge from the daily strife wrought by Covid-19. So many that more green spaces are being considered for inclusion in our urban and suburban areas.  These freshwater ecosystems have long coattails it seems in restoring healthy land-based ecosystems as well.

Angler fishing for shad on Brandywine Creek April of 2020

Angler fishing for shad on Brandywine Creek April of 2020. (Credit: Jon Hurdle/Delaware Public Media)

The Brandywine is not alone in the eastern United States as a beacon of hope for our most threatened ecosystems.  In Maine, the Kennebec River near Augusta saw the removal of the Edwards Dam in 1999—marking the beginning of the era of dam removal in the east.  Following its removal, the return of the Atlantic salmon, sturgeon, and alewives transformed the region’s failing fishing industry into a sustainable model. Since then, rivers seem to have regained a value beyond their industrial use.

Universities have led the way with studies of dam removal on a myriad of rivers in the U.S.  In fact they have been at the forefront of dam removal by suggesting which dams on which rivers should be removed or modified first to restore these important habitats to as close to healthy as possible in the shortest time frame. Cornell University’s New York State Water Resources Institute (NYSWRI) has catalogued 1,600 dams for removal along the Hudson River’s tributaries. Citing that fact that many of these dams no longer perform the duties they were built for or the state of disrepair they are in currently, the NYSWRI is teaming with not-for-profit groups such as Riverkeeper to encourage state agencies to fund dam removal.  The Department of Environmental Conservation in NYS has an annual fund aimed at restoring estuary and freshwater ecosystems including dam removal to communities through grants.  Grants of $40,000 have been made to several municipalities for such projects.

With the return of anadromous fish species to their traditional headwaters the birds, snails, mussels, and predators return in kind.  These freshwater ecosystems represent the tip of the spear of rewilding.  Let’s see these remarkable conservation efforts multiplied tenfold in the next decade to ensure 30 x 30.  In 2023, the series of 4 dams on the Klamath River of Northern California and Southern Oregon are scheduled to be removed in what will be the largest dam removal project in U.S. history.  We need to accelerate the removal of these outdated and useless dams.

Many obstacles need to be overcome before then, but nothing leads to success like success.  These stories of conservation victories should fuel us to do even better.  Our fate and the fate of our beloved fellow beings depend on such victories.

For more information on dam removal efforts and how to get involved, see:

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Chris Bolgiano - February 8, 2021

Hi, Jason, i’m also a member of the ReWilding Council and am researching Legacy Sediments in the East, with a focus on the deforestation of the Appalachian Mountains ca. 1880-1930 and the massive erosion following it. Much and perhaps most of that sediment was captured behind mill dams, which were numerous on every suitable stream from the early 1700s to the early 1900s. Since the abandonment and failure of those dams, that sediment, now called legacy sediment, has been moving downstream burying pre-settlement streams, wetlands and flood plains and creating high stream banks that continue to erode, especially during freeze and thaw. It is one of, if not the biggest, source of sediment coming into the Chesapeake and other eastern Bays. I’m just wondering if legacy sediment been considered during the planning for dam removals, and if so, how? Thanks for any info. -chris

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    Jason L Kahn - February 10, 2021

    Hello Chris,
    That’s an excellent question. It’s a problem for sure. My only experience with this problem is the GE Vs. NY DEC and EPA case about dumping of PCB’s in to the Hudson River. GE argued that keeping the sediments in the river was preferable to dredging them up and releasing the pollutants back into the water column. GE’s argument was flawed in that the sediments are always in motion. Not all at once, but incremental due to tides if the river is an estuary. In all streams the sediments fall out of suspension in times of low flow and are swept up into suspension at high flow and spring flooding stages. The higher and longer duration the flow the higher the volume of sediments that gets moved down stream.
    I guess the big question is where does all the sediment go. Ultimately to the ocean basins, but how long it takes to get there is the big question. To be honest I really don’t know enough about this issue and I will look into it more deeply. What I do know is that if left alone riverine systems tend to take care of themselves and establish a stable baseline eventually. The Chesapeake is a special case however. It has been damaged on so many fronts for so long it seem mean to put it through this, even for a short time.
    Thanks for the thoughtful question.
    Jason

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