Calculating Piped Spillway Capacity
Calculating Piped Spillway Capacity
(OP)
I am doing a spillway analysis for a small pond/dam. The spillway is a 24-inch pipe. I understand how I would calculate the rating curve if it was a short culvert with a known tailwater (or range of tailwater levels). What if the spillway pipe extends thousands of feet before it gets to an open water body (ditch or something)? What if the spillway is infinitely long (stays in a pipe forever)? Can a program like HY-8 handle this kind of situation, or is it only for "short" culverts, and if so, how would you define "short"?





RE: Calculating Piped Spillway Capacity
I haven't used HY-8.
Theoretically,
an infinitely long 24 inch diameter pipe, if it is steep and the discharge is below the full flow capacity, will flow partially full. It will have supercritical flow. Any tailwater, in such a case, will have no effect on the flow.
RE: Calculating Piped Spillway Capacity
In my opinion, connecting the spillway for a dam directly into a long storm drain is not advisable. I would discharge the spillway into a stilling basin and then let it flow into your storm drain system.