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QGIS SWMM Junctions Set Attributes: Difference between revisions

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<li>'''Input Subcatchments [optional]:''' The subcatchments layer(s) that the node(s) receive flow from.
<li>'''Input Inlet Usage Layers [optional]:''' The input inlet usage layer(s) that the node(s) are connected to.
<li>'''Input BC Connection Layers [optional]:''' The BC connection layer(s) that connect the node(s) to the 2D domain.<br>
<li>For information on the other input parameters, refer to the <u>[[QGIS SWMM Junctions Set Attributes#Recommended Settings|Recommended Settings]]</u> section.
<li>'''JunctionAtts:''' Determines the location and filename of the output junctions layer.
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The recommended settings for junctions within the 2D domain depends on whether the node receives flow from a subcatchment and whether and how the node is connected to the 2D domain. <br>
'''Note:''' It is recommended that Ymax be set to 0.0 for all junctions. SWMM will set Ymax to highest soffit of connected conduits.
<br><br>
'''Junction nodes receiving subcatchment flows:'''<br>▼
The recommended settings allow any discharges unable to be conveyed through the node to immediately enter the 2D domain. These discharges are reported as flooding by SWMM.<br>
::*Ysur = 0.0 (forced)▼
::*Apond = 0.0 (forced)
<br>▼
 
'''Junction nodes not receiving subcatchment flows:'''<br>
It is recommended to allow ponding (set Apond >0). This will allow the head in the node (including pressure head) as a water level. If the water level in the node exceeds the water level in the 2D domain, there will be a flow from the 1D domain to 2D domain.<br>
<br>
 
*'''Junction nodes connected to 2D with an inlet:'''<br>
:When nodes are connected through an inlet, either Ysur (surcharge depth) or Apond (area of ponding) can be used to allow the pressure head to exceed Ymax (by default highest adjacent conduit soffit). Using a positive area of ponding may enhance stability. When used, Apond should represent the manhole shaft or a small area. A larger area may enhance model stability but may artificially attenuate discharges. If Apond is non-zero, Ysur is ignored.<br>
:*Ysur = 0.0, if ponding otherwise higher than expected depths to prevent flooding.▼
:*Apond = Manhole area
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*'''Junction nodes connected to 2D with a HX boundary (no inlet):'''<br>
:When nodes are connected through an HX boundary such as culverts through an embankment, it is recommended to set Apond (area of ponding) to the approximate area of connected cells. A larger area of ponding may improve stability but may artificially attenuate discharges. This will depend on the model cell size. Generally, a typical value is chosen that is reasonable for most of the connections and any significantly larger or smaller structures can be modified on an individual basis. <br>
:*Ysur = 0.0
:*Apond = Typical area of connected 2D cells (higher values may aid stability).
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*'''Junctions not connected to 2D domains:'''<br>
:Flood losses would be lost from the model resulting in mass losses and inaccurate results. Prevent by allowing ponding or making surge elevation high.<br>
:Option #1:▼
::*Ysur = higher than expected node depths▼
::*Apond = 0.0
:or Option #2:▼
::*Ysur = 0.0 (ignored)
::*Apond = (positive number)
<br>
▲<brol>
<li>'''General Options:'''
:*'''Maximum Depth Option (Ymax):'''
::*Set to 0.0: Initializes the Ymax for all junction nodes to 0.0. This option may be overwritten for nodes connected to inlets.
::*Leave as is: Leaves the Ymax value as is for all junction nodes. This option applies for 'Edit Feature In-Place' only.
▲:*'''Junction nodesNodes receiving subcatchment flows option (if connected to 2D):'''<br>
::*Based on options selected below: Options set below are applied.
::*Set Apond = 0.0; Ysur = 0.0 (overwrites options below): Forces subcatchment outlets to yse 0.0 for Ysur and Apond (turns off ponding). When ponding is off, node surcharging is reported as 'flooding' to SWMM and is immediately transferred to the 2D domain.
<li>'''Nodes connected to the 2D without inlets (through embankment culvert):'''
▲::*'''Ysur =:''' 0.0 (forced)
:*'''Apond:''' Approximate area of connected 2D cells. A larger area may improve stability, but may artificially attenuate discharges.
<li>'''Nodes connected to 2D with inlets (underground pipe network):'''
:*'''Maximum depth (Ymax) option (overwrites general setting):'''
::*Set to inlet elevation - node elevation: Sets the Ymax value to the inlet elevation minus the node elevation.
::*Use global option: Sets the Ymax value based on the settings selected in the 'Global options' section.
▲:*'''Ysur:''' =Set to 0.0, if using ponding. otherwiseOtherwise, set to higher than expected depths to prevent flooding.
:*'''Area of ponding:''' Set to the manhole area.
<li>'''Nodes without a 2D connection (underground pipe network):''' When a node is not connected to the 2D, flood losses will be lost from the model resulting in mass losses and inaccurate results. To prevent this, allow ponding (option 1) or make the surcharge depth high (option 2).
▲:*Option #1:
::*'''Surcharge depth:''' Set to 0.0.
::*'''Area of ponding:''' Set to some positive value.
▲:or *Option #2:
▲::*Ysur'''Surcharge =depth:''' Set to a value higher than expected node depths.
::*'''Area of ponding:''' Set to 0.0.
</ol>
 
== Example ==
Retrieved from "https://wiki.tuflow.com/QGIS_SWMM_Junctions_Set_Attributes"