| Product(s): | StormCAD, SewerGEMS, CivilStorm, OpenRoads Designer |
| Version(s): | All |
| Area: | Calculations |
Problem
When using the GVF-Rational (StormCAD) solver, how is the depth and spread calculated for an inlet whose Inlet Type is set to "Full Capture" of "Percent Capture"?
Solution
Using the GVF-Rational (StormCAD) solver, when the "Inlet Type" of a catchbasin is set to "Percent Capture" of "Full Capture", the depth and spread are calculated by solving the Manning equation using the gutter dimensions and the surface approach flow.
The following screenshot shows the use of our FlowMaster product to verify.
A note on in-sag inlets
When an inlet is in-sag, it means that it will capture 100% of the surface flow, so it would only make sense to use full capture or a catalog inlet.
When the Inlet Location is set to In-sag and the Inlet Type is set to Full Capture or Percent Capture, the GVF-Rational solver still uses the longitudinal slope and Manning n values (which can be seen and edited from the Catchbasin Flextable) to calculate the depth and spread with the Manning equation. It must make this assumption in order to estimate a depth and spread, which can be considered as the depth and spread at the pavement slope that approaches the sag point.
If you are concerned with depth and spread for in-sag inlets, it is advisable that you use a catalog inlet so that the depth and spread are calculated with the HEC-22 equations based on orifice or weir flow.