AutoCAD Civil 3D - Stormwater

AutoCAD Civil 3D - Stormwater

New Member
Posts: 2
Registered: ‎12-13-2012
Message 1 of 2 (261 Views)

Orifice calculations in Hydraflow Hydragraphs

261 Views, 1 Replies
12-13-2012 01:35 PM

I can't seem to confirm the discharge table that hydraflow produces in hydraflow hydragraphs.  I think I understand the equation itself (it's been a while since I took hydraulics), but can't understand where I'm making my error (if I am).  Normally I trust the stage/discharge curve that hydraflow produces, but the City Engineer is asking me to confirm the values by hand and show them on the plans.  Is there a link to an detention pond example that shows how a curve (the outflow values) was generated (confirms the discharge table at various elevations)? The equation is on page 85 of the users manual.

Distinguished Contributor
Posts: 1,299
Registered: ‎03-07-2006
Message 2 of 2 (233 Views)

Re: Orifice calculations in Hydraflow Hydragraphs

12-24-2012 08:26 AM in reply to: tjc4

Try going to the table tab under ponds and hit the little plus on the lower right to expand the table.  Print table.


What C value are you using in the manual calculations?  It is normally around 0.6 for orifices.


Are you taking into account the back water from the lower pipe?


Can you post a pdf of your pond outlet configuration?

Ann Wingert, P.E.
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