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Re: stage storage for underground pipe with slope
If this is for a SWMM model application, I believe that SWMM will do this calculation for you. Just input the pipe at the desired slope with the downstream end at the node where you want to model the storage.
Otherwise, you could probably figure it out youself. The volume will be prismatic, so (I think) that Simpson's rule will yield an exact result, which reduces to the same equation as a cone because the far end is a point.
Vol = 1/3 * L * A
A = end area of a circular segment.
A = R^2*acos(1-d/R) - (R-d) *sqrt(2*R*d-d^2)
and of course L = d/S
S is slope, d is depth, R is pipe radius.
Someone correct me if I'm wrong, but I think this will at least give an excellent approximation.
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