	Applies To
	Product(s):	StormCAD, Civilstorm, SewerGEMS
	Version(s):	08.11.XX.XX, 10.XX.XX.XX
	Area:	Output and Reporting
	Original Author:	Mark Pachlhofer, Bentley Technical Support Group

Problem

How does sub-surface piping surcharge or overflow conditions impact the capture efficiency of an inlet?

My subsurface conduit system is surcharged, but upstream inlet capture does not change and does not appear to be influenced by the tailwater effect.

Problem ID#: 46440

Solution

The above-surface gutter system is completely independent from the subsurface piping system in StormCAD (GVF-Rational solver). A change to the sub-surface hydraulics will not impact inlet capture. In other wise, a backup causes by a bottleneck will not be "seen" as a tailwater against the inlet opening and no reduction in the inlet's capacity will be seen.

StormCAD basically assumes that you will design the system such that it will not flood/surcharge, and some simplifications are made in a flooding condition, which you can read about in the article further below.

If you need to assess surcharging/overflowing conditions, you'd need to use a dynamic numerical solver, such as the Implicit or Explicit solvers available in SewerGEMS and CivilStorm.

Overflow or Flooding Impact on Inlet Capture for StormCAD (GVF-Rational solver)

Problem

Solution

See Also