SWMM - Links - Weir

Weirs are used to model outlet and diversion structures in a drainage system. Weirs are typically located in a manhole, along the side of a channel, or inside a storage unit. They are represented internally in SWMM as a link connecting two Nodes, where the dam itself is placed at the node a amount. A gate can be included to prevent backflow.

In addition to the shared properties of SWMM links, Weirs also have the following properties:

• Weir
  • Discharge Coefficient (DischargeCoef, Double) - Discharge coefficient for flow through the central portion of the Weir
  • Weir Curve (WeirCurve, ObjectId) - Optional Weir Curve that allows the central discharge coefficient to vary depending on the manometric head
  • Retention Device (FlapGate, Boolean) - YES, if the Weir has a gate that prevents backflow,
    NO if not
  • Can Overload (CanSurcharge, Boolean) - YES if the Weir can overload (has a water level upstream higher than the height of the opening) or
    NO if you can't
  • Inlet Offset (CrestHeight, Double) - Height from the spillway base to the inlet invert elevation
• Type of Weir
  • Type of Weir (WeirType, Enum) - Five types of Weirs are available, each incorporating a different formula to calculate flow as a function of area, discharge coefficient and head difference across the Weir:
    • Transversal - rectangular shape
    • Side flow - rectangular format
    • V-notch - triangular shape
    • Trapezoidal - trapezoidal shape
    • Highway - wide crest rectangular dam used to model road crossings
  • Road Width (RoadWidth, Double) - Vertical height of the spillway opening
    Use when the spillway type is Highway
  • Road Surface (RoadSurf, Enum) - Type of road surface
    Use when the spillway type is Highway
  • Side Slope (SideSlope, Double) - Slope of the side walls (width/height)
    Use when the spillway type is trapezoidal
  • Discharge Coefficient (EndCoeff, Double) - Discharge coefficient for flow through the triangular ends of a TRAPEZOIDAL weir
  • Contractions (Contractions, Enum) - Number of final contractions for a TRANSVERSE or SIDE dam whose length is shorter than the channel in which it is placed. Either 0, 1, or 2, depending on whether no end, one end, or both ends are chamfered to the sidewalls
  • Side Slope (SideSlope, Double) - Slope of the side walls (width/height)
    This applies when the weir type is trapezoidal or V-notch
  • Horizontal Length (WeirLength, Double) - Horizontal length of the Weir opening
  • Vertical Height (WeirLength, Double) - Horizontal length of the Weir opening
    This is a property that depends on the geometry of the Weir, so it must be tied to its geometry, for example:
    
    
    In the image above, Height is defined in the properties frame of the model:
    
    

To view the properties of a Weir in SOLIDOS, use the tab Properties or use the command SPROPS:

Note: You must click the at the top of the screen.

If it is not visible, it means that the network is not enabled for SWMM. Enable it in your properties: