Glen Canyon was slightly different because there was no "emergency spillway" in the same way that Oroville has. Glen Canyon simply had 2 giant spillways that bo

Glen Canyon was slightly different because there was no "emergency spillway" in the same way that Oroville has. Glen Canyon simply had 2 giant spillways that both needed to be in use but were both getting torn apart by cavitation. They ended up adding plywood along the top of the spillway gates to give themselves a little more reservoir capacity to wait out the flooding upstream but honestly they just got lucky. The only option they had at Glen Canyon if they exceeded the plywood barrier would have been to let water flow down the main spillways and possibly damage the dam.