Problem

Where is the 'Gutter Depth' result field measured from, when using the GVF-Rational solver?

Is it measured from the bottom of the local depression or from the gutter depression?

Problem ID#: 46782
Reference #: 388504

Solution

As of the CONNECT Edition, the gutter depth results field is always measured from the bottom of the local depression. This can differ from other applications such as FlowMaster, which does not account for the local depression in the gutter depth figure.

Note that during the calculations, when the orifice-controlled depth is compared to the weir-controlled depth, this comparison is done before the local depression height is added to produce the final reported gutter depth.

Note also: in general, the depth and spread at an on-grade inlet is measured from the upstream side of the inlet, where spread is highest (before some or all of the upstream gutter flow is captured by the inlet).

Earlier Versions

In earlier versions, the 'Gutter Depth' field would only take local depression into account if the spread was less than the depression width. The same logic also applies for the gutter depression. It is only taken into account in this result if the spread is less than the gutter width.

Note: if you see negative calculated depths reported even though the spread is less than the local depression width, this could be due to unique circumstances. In this case, your inlet is likely oversized and you should try selecting a smaller size.

See Also

Unexpected spread and depth results for a curb inlet in sag with local depression

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

Depth and spread calculations for grate inlet in sag