As discussed in Section 3.12.1, pit channels are created from nodes (also referred to as pits) that have the Channel_Type attribute (see Table 4 .10) set to C, R or W.
The pit channel ID is given a “.P” extension based on the ID assigned or specified to the node. The upstream (ground) node ID of the pit channel is given a “.0” extension. The ground elevation is specified in the Upstream_Invert attribute, and the bottom elevation of the pit or manhole is specified in the Downstream_Invert attribute. The Topo_ID attribute can be used to specify if this pit is to be connected to an overland 2D domain (this saves having to create 2D SX links in a 2d_bc layer).
Pit channels are zero length channels designed to convey water to/from a 2D overland domain to a 1D pipe network. They do not contribute to any storage in the system (noting that the Length_or_ANA attribute is used to specify the surface area or storage of the pit or manhole).
If a pit channel cannot be connected to an overland 2D domain (because, for example, it does not fall on an active cell), a WARNING is issued (see Section 6.2.2) and the pit channel will remain unconnected.
In the various 1D output and the 1d_nwk check files, the pit channel is displayed as a channel, not a node. The display length of the channel is, by default, set to 10 m, however, this can be changed using Pit Channel Offset.
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