The US has hundreds of thousands of dams on the rivers, some big, some small. The Riverkeepers, Native Americans and environmentalists have been pushing to remove old dams to restore watersheds.
Since 1998 more than 1,500 dams have been removed across the country, according to American Rivers, including two large hydroelectric dams along the Elwha River in Washington state, which were imperiling wild salmon populations, and many more small ones such as the mill dams on the tributaries of the Hudson.
One example is on the Quassaick in New York State. George Jackman, an ecologist with The Riverkeepers, calls dams along it “ghosts of capitalism.”
For him, the dams are an ugly reminder of a dreadful past. “This was a foul place,” says Jackman. When the dams powered nearby industries, he says, “there were no environmental laws. There were no child labor laws. There were no labor unions. There was no Clean Air Act, no Clean Water Act. This was a place of death.”
These old dams can breach in an uncontrolled fashion, flooding nearby communities. They fragment habitat and collect sediment. It’s especially hard for cold water fish that can’t reach colder water upstream. It’s astounding how fast they find their way after a dam is removed.
The evidence suggests that migrating fish find their way to their cool-water spawning grounds, even when their routes have been blocked for many generations. A study published in the journal BioScience found that “upstream migration was evident within weeks or months” after small dams were demolished in the midwestern and eastern US, and “up to 95% of all species found downstream of the dams migrated upstream within 1-3 years”.
In some cases, the fish move in much quicker: when a dam was removed from the Wynants Kill near Troy, at the upper end of the Hudson River estuary, within days underwater cameras recorded thousands of silvery river herring swimming into the newly opened stretch of river.
https://www.theguardian.com/us-news/2022/nov/04/push-to-dismantle-dams-us-rivers-environmentalists
Dam removal is not just happening in the US. In 2021, Europe removed over 200 barriers.
Darcy Hitchcock 
Woo-HOO! 👍👌🎉