Nodes and Links

In a general sense, nodes are points or junctions at which links join together to form a network.

In an urban stormwater drainage system, nodes can represent upper extremities of a pipe or channel system, junctions, places where the characteristics of conduits change and outfalls. Links, which are vectors having a direction, represent pipes, channel reaches and overflow routes.  The term reach is often used interchangeably with link, particularly for open channel sections.

As shown in the above diagram, networks can be tree-like, with only one outlet from each node, and looped.  A system in which there are two outlet pipes or channels leaving a node is equivalent to a looped system. Under extreme conditions, flow reversals may occur in outlets from pits. DRAINS can model looped systems both in the unsteady flow calculations employed in the Lite and Full Unsteady hydraulic models.  However, the model only allows one pipe outlet from a detention basin.  

The water that flows through a stormwater drainage network must be introduced through sources and removed via sinks. In DRAINS the sub-catchments act as sources of stormwater runoff and the outlet or terminal nodes as sinks.

In DRAINS, bridges, culverts, headwalls, detention basins, and most importantly, pits, are modelled as nodes, as shown in the the following section of the Toolbar: 

The first tool is a simple node, , that can take different forms, depending on its position in a network.

Similarly, there are various types of link, , representing pipes, prismatic channels, irregular channels, multi-channels, overflow routes, and storage routing reaches.

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