The Canyon Lake dam, near Canyon City, Texas, overflowed its spillway for several days in 2002, cutting a large gorge beside the dam. People can take tours of this gorge, and the cut made through bedrock. During the tour, the guide tells that studies of this gorge reinforce the thought that the Grand Canyon was cut quickly by flow from a glacial lake giving way. See: Canyon Gorge
It wasn’t just glacial lakes which dammed the Colorado River. Volcanic ash and magma also dammed the river and then collapsed to release the lakes behind those natural dams.