Why is it that no matter how large the inlet on grade is the gutter spread always remains the same?

Product(s): SewerGEMS, CivilStorm, StormCAD
Version(s): CONNECT Edition, V8i
Area: Output and Reporting

Problem

Why is it that no matter how large the inlet on grade is the gutter spread always remains the same?

Solution

HEC-22 inlet computations are concerned with when the gutter spread is maximum, which is immediately upstream of the inlet (see image below).  Just downstream of the inlet, the spread is at its minimum because most, if not all, of the water has been intercepted.  The spread is calculated for the flow in the gutter immediately upstream of the inlet, so the size of the inlet does not impact the width of the  gutter spread.  To remedy this situation, try increasing the size of the inlet(s) upstream of the inlet you have been working on.

 

See Also

Order of automated design priorities for StormCAD (GVF-Rational) and SewerCAD (GVF-Convex)

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