This isn’t an isolated occurrence: Ladders and elevators along other Atlantic Coast rivers have failed as well, and as badly for shad and other migratory species. But the four-step obstacle course on the Susquehanna is especially harmful, cumulatively confounding and slowing the migrations, so that very little reproduction actually occurs. Nevertheless, the federal government is doubling down on these failed approaches, with a new plan that makes at best minor changes to the existing, futile array of fish-passage devices.

The destruction of enormous fish migrations is bad enough. But it gets worse. Because the sprawling Susquehanna drainage is unusually sediment-laden, the reservoirs behind each dam have been filling with voluminous quantities of sand and muck; three of them have reached their sediment-holding capacity and the fourth, the Conowingo Reservoir, is quickly approaching it. If nothing is done soon, the sediment will no longer be trapped and will travel past the dams into the Chesapeake Bay.

This would mean ecological devastation for the bay, which is already overenriched and would choke on the nutrient-packed sediment suddenly thrust on it. The only other answer is expensive, continuing dredging — and blind hope against an erosive storm or hurricane that would overload the dams and release the sediment.

With all this in mind, policy makers need to take the only responsible step and remove the dams. True, they produce valuable electricity that would be tough to replace. But there are alternatives. By our calculations, a solar park built on the drained floor of the empty Conowingo Reservoir could allow the river to run beside it and replace the 575 megawatts the dam generates. And low-head hydropower arrays — devices that pull energy from the river without impeding it — could add even more.

It’s hard to look at something as large as a dam and not think of it as a permanent part of the landscape. But that’s an illusion: Eventually the dams will deteriorate, and will someday have to be removed for safety reasons. Indeed, across the country people are starting to reckon with the environmental costs of large hydropower dams, and several have been removed already. In 1999, the federal government allowed the removal of the Edwards Dam on Maine’s Kennebec River, a precedent-setting action that brought much of the river back to life.