Conduits

The following types of conduits are available in InfoWorks ICM, all of which join two nodes:

• Conduit - a pipe or open channel - SWMM and InfoWorks networks
• Conduit 2D - typically a culvert and used for 2D modelling - InfoWorks networks only
• Linear drainage 2D - typically a linear gully and used for 2D modelling - InfoWorks networks only
• Culvert - a conduit that conveys flow through an embankment or past some other type of flow obstruction (as defined in the Hydraulic Design of Highway Culverts, Third Edition) - InfoWorks networks only

The properties which define these types of conduit are described in the Conduit Data Field (InfoWorks) or Conduit Data Fields (SWMM) topic.

The cross section of a conduit is defined as a Shape object. You can create new conduit shapes or re-use an existing shape by selecting it from the Shape ID field for an InfoWorks conduit or the Shape field for a SWMM conduit.

Hydraulic model characteristics

The following characteristics apply to InfoWorks conduits:

• The conduit is considered to be prismatic. That is, the cross section is the same from the upstream end to the downstream end.
• InfoWorks ICM uses the equivalent grain roughness concept (HR Wallingford and D.I.H. Barr (1994)) to determine the composite roughness of the cross section.
• For the area, width and perimeter, an open shape assumes a constant side slope based on the two width entries below channel height. If the side slope has a negative value, the software uses vertical sides for the geometric calculations. It is worth noting, however, that the conveyance for an open shape (built-in or user-defined) does not increase once you reach the conduit height. If you do anticipate your shape overtopping, it would be better to use a channel or river reach to get an increasing value of conveyance.

For information about the characteristics for SWMM conduits, see the latest version of the SWMM Reference Manual (Hydraulics), which can be downloaded from the EPA website.