damAn increasing number of dams are being removed across the United States. In the rivers where dams used to stand, marine life is returning and the natural ecosystem is resurgent. 

The U.S. has a proud tradition of dam-building. As Bill Clinton’s Secretary of the Interior Bruce Babbitt has observed, “on average, we have constructed one dam every day since the signing of the Declaration of Independence.”

Yet dams disrupt the natural flow of rivers, degrade their ecosystems and deplete fisheries. By slowing water flow, dams increase water temperatures and can damage or destroy sensitive marine species. By creating irregular surges (in lieu of a natural flow), dams disrupt the seasonal cycles of soil and vegetation. Creating blockages in the river also causes the accumulation of sediments, debris and pollutants.

Finally, according to American Rivers, a domestic watchdog group, many dams no longer serve their original purposes and are now unsafe or obsolete.

Armed with all of this evidence, the federal government has been removing dams across the nation. In the past 20 years, about 1,150 of America’s 85,000 dams have been dismantled. “It used to be a crazy idea,” says Amy Kober, director of communications for American Rivers. “Now it’s accepted.”

Five years ago, an 8 meter high concrete wall blocked Stabler, Washington’s Trout Creek. The dam was removed in 2009 and since that time the endangered steelhead trout have been able to spawn in ever-increasing numbers. Patrick Connelly, a biologist at the Columbia River Research Laboratory, says the steelhead population has doubled in the area.

The Condit Dam was deconstructed on Washington’s White Salmon River in 2011. In that case, so much sediment had built up behind the dam that it was impossible to cart it away, as had been the case in Trout Creek. Whereas Trout Creek had built up some 42,000 cubic meters of silt, Salmon River contained forty times as much. When the dam was detonated, the slurry that gushed forth was 28 percent sediment by volume. Much of that sediment was completely washed away within the first three hours of the detonation. You can watch a time-lapse of the event below:

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