The outlet is a command to control the outflow of storage.

They provide a means to simulate specific head-discharge relationships that cannot be adequately characterized by pumps, orifices, or weirs. In VOSWMM, outlets are represented internally as links connecting two nodes, and the option for a flap gate can be incorporated to confine flow to a single direction.

Outlets associated with storage units are operational across all flow routing scenarios. In the absence of attachment to a storage unit, they are restricted to use in drainage networks analyzed using Dynamic Wave flow routing.

The discharge flow through an outlet is determined by a user-defined rating curve, showcasing its dependency on either the freeboard depth above the outlet’s opening or the head difference across it. Control Rules offer the flexibility to dynamically adjust this flow based on specific conditions.

Parameter Name Description Default Value
NHYD Hydrograph number.
NAME Name of the component.
From Node The name of the from node.
To Node The name of the destinated node.
COMMENT 1, 2, and 3 Comment for the command.
Tag Optional category or classification.
System Type Specifies the junction’s system type, whether it belongs in the overland, storm, or sanitary system. Blank
Height [m] Height of Outlet (ft or m). 1
Width [m] Width of Outlet (ft or m). 1
Inlet Offset [m] Depth or elevation of Outlet inlet node invert. 0
Flap Gate Select YES if the weir contains a flap gate to prevent backflow. NO
Rating Curve Method of defining a flow (Q) as a function of freeboard depth or head (y) across the outlet. *Functional_Depth
Inflow Rating Curve Check on this box means the rating curve of this outlet link will be obtained from the assigned manhole inflow rating curve tool.
Coefficient Coefficient (A) – for the functional relationship between depth or head and flow rate. 10
Exponent Exponent (B) – used for the functional relationship between depth or head and flow rate. 0.5

Different types of rating curves are available.

  • Functional Depth
  • Tabular Depth
  • Functional Head
  • Tabular Head

Key input parameters for an outlet encompass:

  • Names of its inlet and outlet nodes
  • Height above the inlet node invert
  • Function or table detailing its head (or depth) – discharge relationship.