Last fall I built a dam for a 1/4 acre or so pond near my yard, which was to serve as a grow out pond for fish to be added to my big pond. I put the finishing touches on it this spring. In all that time we had little or no run off so it sat basically empty. Thursday night we had 3.5 inches so I was delighted to wake up and find it full (though it was mostly muddy water and cornstalks). The dam was holding, though I needed to raise the water level a little which I could easily do by adding to the stand pipe. Then Friday evening we got two more inches of rain in 45 minutes. Here's what I woke up to find Saturday morning.
And here is a view from the back.
I can't say that I was terribly surprised. I am trying to make a quarter acre pond fed with about 50 acres of run off. The white pipe was meant to control the level during light run off. It also has a gate valve so that I can drain the pond every couple of years to clean out sediment from the neighbor's field. In the second picture you see a 30'x10" plastic culvert. It was meant as the overflow after the stand pipe. It obviously couldn't handle this amount of water and when water started going over the dam it was washed out and ended up about 300 feet downstream. My other problem was lack of a proper spillway. I didn't have a transit/level and kept procrastinating about going off to rent one (I have on ordered now) and so the lowest part of the dam was the middle over new dirt instead of off to a side.
I'm not real upset about this and fortunately there were no fish in it yet. I plan to make the dam thicker, add another culvert for an overflow and a properly sized and located spillway, plus a few other improvements I could see needed to be made. Maybe this small of a pond with this much potential water shed is asking for trouble.
