[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/05/EW-06-18-12-Dam-Removal.mp3|titles=EW 06-18-12 Dam Removal]
John McPhee once wrote that for environmentalists, there is a dam “at the absolute epicenter of Hell.” Dams built in the twentieth century, impeded salmon and other migratory fish from reaching their spawning grounds.
It almost seemed as if rivers, no longer important for navigation, were expendable. Dams fragmented river ecosystems. To add insult to injury, many of those dams did not live up to their economic promise.
That’s why some aging dams are now being decommissioned instead of rebuilt. This process is intended to re-establish the natural flow of rivers, bringing their ecosystems back to life. But dam removal does have some unintended consequences.
Martin Doyle, a professor of river science and policy at Duke University, explains…
“We got going by doing what’s called the “blow and go” approach, where we would go in with some kind of explosives to fragment the structure and then follow up with heavy machinery to just dig out the dam essentially almost as fast as we could. When we do that, any sediment, toxins or pollutants that are stored in the reservoir or in the impoundment get flushed downstream very quickly. So we’ve started to shift and try some ways that may allow us to stabilize some of the sediment in place. So now we kind of have the “creepy crawly” approach, where we cut out a little bit in the middle and then let the reservoir sit there for a period of time and de-water the reservoir, plant some vegetation to stabilize some of the sediment, do it more gradually to try to reduce the shock to the system that the “blow and go” causes.”
As the age of dam building draws to a close, this research will help us to decommission dams in the best way possible for the ecosystem’s health.
Web Links
Martin Doyle Research Group at Duke
http://sites.nicholas.duke.edu/martindoyle/
Photo, taken on August 2, 2010, courtesy of Matt via Flickr.