Need help figuring out what size pipe I need for dam. I live in South Alabama. The average ran fall is 57 inches annually. Soil type is Clay. Been trying to figure out the watershed for pond site. Also there is a small stream that will feed the pond.
Hard to know without watershed numbers. Given the 57 inches, clay soil, and small stream, I'd say you should err on the side of large rather than small. Emergency spillway should be for emergencies, not common occurrences.
You get a lot of bang for your buck by upsizing. For instance, my pondbuilder wanted an 8 inch pipe, but fortunately had to install 9 3/8 inch. That means close to 40 percent greater maximum flow, obviating the need for the emergency spillway outside of the most extreme events!
