This pipe extends out into the pond.
It goes up and over the dam
and is connected to a pump.
The pipes go into the ravine on the back side of the dam. FYI, the pipes are put together with connectors and silicone, but they also have straps on them (the orange strap in the picture) to help hold them because the water pressure is so great, it will pull the pipes apart. The straps are an extra safeguard against that.
The pump is used only to start a siphon. Once that gets going, the water flows up, over, and down, pouring out into the stream behind the dam.
This systems has brought the pond level down so that it is no longer threatening the spillway or dam. When the ground dries up a bit, Tom is going to put in permanent system that will siphon the water out when it gets too high. The permanent system will not go up and over the dam, though, it will be buried under the spillway.
I doubt will have this much rain again for a long time, but if we do, we will be prepared.