Sounds great rock creek.
I have to amend my statement about the siphon being up to job in my pond though. About a week ago we got 2.5 inches of rain overnight and when I woke up the water was going over the (emergency) spillway. The siphon had started but just couldn't handle the flow.
When I got to the pond it was about 6 inches from breaching the dam and rising fast. I grabbed my shovel and started digging out the spillway. I moved about a yard of wet clay until the outflow was more than a foot deep and about 4 feet wide. I stopped the rising water when it was close to 3 inches from the top of the dam. Of course the dam is too new to have anything growing on it and it was very soft.
Between digging out the spillway and the inflow slowing down I saw that the level was finally dropping. I walked down the dam and I saw that the heavy flow over the spillway was cutting into the back of the dam pretty heavily. I had lost about 5 feet and the slope was vertical in the worst place.
I grabbed the shovel again and started moving the clay back into the trench I had made in the spillway. Naturally it's harder to stop the flow than to increase it.
I decided to play beaver and started placing large branches across the flow and then filling in the spaces with the best clay. After maybe a half hour of this I managed to stop the water.
I walked over to the siphon and closed the vent valve. I drained the pond down about 2 feet below full pool. Since this was the second time I had to labor to save the dam in the past few weeks I was tired of it. The pond came back up to full pool within a few days anyway.
I think the watershed for this pond is pretty big. I plan on removing the four 90 degree elbows on my siphon and replacing them with four 22.5's. Now that the emergency spillway is a little drier I'm going to widen it and put that dirt on top of the dam. I noticed that most dams around here are only about 1 foot higher than the emergency spillway and I want more.
