Yessir. The areas are the same. I'd think a 6" would/could flow more as the 4x3"dia pipes have double the wall surface, and especially with corrugated pipe, the friction losses are significant. Were you suggesting lotta little pipes be better?
The 2" drain was flowing more than the 6" corrugated, but that drain comes off the bottom of the pond under pressure. I didn't feel I ever got the 6" pipes into a solid siphon like the 4".. you can see the difference in how full the exit dia is and velocity coming out. The corrugated pipes all ran the same elevation drop. But they all rose above the water level going over the hump, so there was some kind of siphon. As everyone says, it all depends.
The 2" drain was put in with the pond. I went down with a 100' roll of 4". I saw it wasn't enough, as you can clearly see in the video. So I went to town and bought a roll of 6". It was coming down, then I heard they predicted rain again today and I spooked and went and bought another 6". In the absence of my properly installed 12" overflow, I do the best I can on my own.
