reporting invert of a culvert with reverse slope

Question

reporting invert of a culvert with reverse slope

pjhealy (Civil/Environmental)

(OP)

23 Jan 13 13:07

I would like you to confirm that this is an error in reporting and not in the calculations (HydroCAD 8.50). I entered a culvert outlet with a reverse slope from a pond to reflect the possibility that runoff could potentially back up a catch basin to manhole pipe, if the head were high enough. On the entry screen, the pipe has an invert of 571.77, but on the report screen, the invert at the higher end of the pipe is shown. This is causing some friction between myself and a reviewer who is a new HydroCAD user (HydroCAD 10.0). She insists that I have entered it incorrectly, which I have not. Thank you.

psmart (Civil) · Answer 1 · 2013-01-23 17:12:12

The pond outlet summary, under the "Invert" column, shows the elevation at which flow will start to occur. For a culvert, this is the higher end of the pipe. So if the pipe has an adverse slope, the outlet invert will be listed.

If you look at the device details, it also shows the specific inlet and outlet inverts, exactly as you entered them. This detail may have been added after 8.5, but it will definitely appear in the 10.0 report.

However, setting an adverse slope will not induce a reverse flow. The flow will still occur in the direction of the outflow arrow, but the flow will not start until the WSE exceeds the outlet invert. If you really want to model a reversing flow that's another discussion.

Peter Smart
HydroCAD Software
www.hydrocad.net

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reporting invert of a culvert with reverse slope