In SewerGEMS and CivilStorm for the Implicit and Explicit solvers you have the option of the "Arch" shape type. This is simply defined by a rise and span. For the Explicit solver you have the additional option of the Arch Data Type.

In SewerCAD and StormCAD for the GVF-Convex and GVF-Rational solvers you can only use a Pipe-Arch shape as a Catalog Conduit reference. If the conduit is user defined you do not have the option of either Pipe-Arch or Arch.

If you set the conduit type to "Catalog Conduit" you can select, if available, the Pipe-Arch conduit shape which will in turn filter any catalog conduits that are of that type.

Note that if you have SewerGEMS/CivilStorm SELECTseries 2 model which references a Pipe-Arch from the Catalog Conduit library, upon conversion to SELECTseries 3 those references will be converted to User-Defined Arch shapes local to each relevant conduit. The more complex Pipe-Arch shape is only supported by the Rational and GVF-Convex engines. A validation error will occur if the Pipe-Arch shape is used with the Implicit or Explicit engines.

Conversely, if you set up a StormCAD or SewerCAD SELECTseries 3 model (or within SewerGEMS or CivilStorm using the appropriate GVF solver) and the conduit is set to user defined with the Arch conduit shape you will get an error message that will prevent the model from computing. If you receive this error, change the conduit to catalog conduit and select a pipe-arch reference.