Old Man River is More Spry Than We Thought

Researchers have determined that rivers can recover from dam removal much faster than experts thought possible, returning long gone ecosystems to how they once were in record time.

That's at least according to a new study recently published in the journal PLOS One, that closely followed the removal of two dams in Oregon.

The Calapooia River and Rogue River dams were removed in 2009, and subsequently released a massive flood of sediment that had accumulated over the decades. Ecologists had been worried that this sudden release would cause significant damage to both local ecosystems and the river structure itself.

However, the study showed that this really isn't the case. The temporary pulse of damage to the river caused by a sediment release paled in comparison to the decades of degradation, migration disruption, and habitat fragmenting caused by the dam's installation.

"Dams are a significant element in our nation's aging infrastructure," Desirée Tullos, who was involved in the research, said in a recent release. "In many cases, the dams haven't been adequately maintained and they are literally falling apart. Depending on the benefits provided by the dam, it's often cheaper to remove them than to repair them." (Scroll to read on...)

"The processes of ecological and physical recovery of river systems following dam removal are important, because thousands of dams are being removed all over the world," she added.

And she's not wrong. According to the American Society of Civil Engineers, the United States boasts about 84,000 dams with an average age of 52 years. Almost 2,000 of those are considered so deficient that they are not worth the repair costs, and instead have been slated for removal.

By closely monitoring the recovery of Calapooia River and Rogue River dams, they determined that aquatic and insect life at both dam sites recovered and even improved - reverting to natural states in just a single year after removal. In about two years, even the sediment dump they were worried about had washed out and settled.

"In the end, most of these large pulses of sediment aren't that big of a deal, and there's often no need to panic," Tullos said. "The most surprising finding to us was that indicators of the biological recovery appeared to happen faster than our indicators of the physical recovery."