Construction of large dams in the U.S. mostly came to a halt in the 1970s. Many are now unsafe, inefficient or no longer needed, requiring removal—events that geologists and biologists alike will follow closely to observe how these unimpeded rivers and their wildlife respond.
by the numbers
538
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Dams removed in the 90 years before 2005.
548
Dams removed from 2006–2014.
10 million
Cubic meters of stored sediment released on removal of two dams (64- and 32-meter-high structures) in Washington State last year, the largest release to date.
SOURCES: “1000 DAMS DOWN AND COUNTING,” BY J. E. O'CONNER ET AL., IN SCIENCE, VOL. 348; MAY 1, 2015 (dam removals); “THE REMAINS OF THE DAM: WHAT HAVE WE LEARNED FROM 15 YEARS OF US DAM REMOVALS?” BY GORDON E. GRANT AND SARAH L. LEWIS, IN ENGINEERING GEOLOGY FOR SOCIETY AND TERRITORY, VOL. 3. EDITED BY GIORGIO LOLLINO ET AL. SPRINGER, 2015 (sediment release)
Subscribe to Support Independent Journalism
Great science journalism requires human expertise, time, effort and creativity. And it costs money. That’s why I and the journalists here at Scientific American hope you’ll join our community.
When you subscribe, you are supporting staff and freelance journalists who are passionate about telling science stories that are true, important and compelling. Our editors and reporters are often experts in their fields, which means they understand the nuances of big discoveries and can untangle the breakthroughs from the hype. With a subscription, you are also supporting rigorous fact-checking to ensure the words we publish are precise and accurate. And you’re supporting original illustrations, graphics and photos that bring you closer to an advanced laboratory, an ice sheet in Antarctica or a space mission in orbit. You’re helping us craft other types of high-quality journalism as well: Our newsletters are carefully written, edited and curated by staffers you have or will come to know and love. Our Science Quickly podcast is based on original reporting, collaboration with editors and scientists and exacting production.
Subscriptions keep this engine running so we can continue to deliver thoughtful, rigorous and independent science journalism to you. In an era of viral misinformation, this work is crucial. If you value what we do, I hope you’ll consider joining us as a subscriber
