After the Rapidan Dam failed last summer and the Blue Earth River carved a new course through Minnesota Valley, researchers are using drones to survey the area and monitor changes that affect the entire waterway and landscape downstream, MPR News reported.
The project is being led by Phil Larson, earth sciences director at Minnesota State University Mankato, and Zach Hilgendorf from the University of Wisconsin-Eau Claire, who will monitor the area until the summer of next year. They're looking at how the flooding river has cut new channels and cliffs through the area, what's happening to all the sediment being washed away, and the stretches of exposed soil left behind.
"It looks like we're on the moon or something," said Larson, per MPR News.
The Rapidan Dam was an old but still sturdy structure. It underwent "avulsive failure," meaning the water didn't go through it; it went around. During a flood, when water levels were high, the river dug a new channel through the softer earth beside the dam and released the built-up pressure behind the barrier.
"The river just evolved and went over here and said, 'We don't want to, I don't want to deal with the dam,'" Larson said, per MPR News. "'I'm going to cut down over here through this landscape, because it's weaker, softer materials.' So, the river now has been locked into this new course here, and we have this dam just sitting here doing nothing."
That sort of thing is getting more common for two reasons. First of all, America's infrastructure is aging, dams included. The older it all gets without being repaired or replaced, the more likely it is to fail.
Meanwhile, heat-trapping air pollution is making the world hotter, which makes the weather less stable overall. Cycles of drought and flooding, plus heavy storms, are all part of the package. And when those storms and floods hit, they can change the landscape.
In the Blue Earth River's case, that means six Olympic swimming pools' worth of sediment is being pushed downriver. As a result, the river is shallower — between 1.5 and 4 feet when the water is low — and will eventually flow into the Minnesota River and then the Mississippi. The chemical composition, which includes a lot of phosphorus, could damage the environment.
The news isn't all bad. Dam removal creates opportunities for fish that were previously blocked from traveling upstream and now may be able to return again. That could be great for struggling fish populations.
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