Subject: This is how SWMM 5 handles jumps in pipe invert across a node.
The water surface in the node determines the flow in the link, as the depth increases due to upstream inflow eventually the downstream link will start flowing.
Note: What Node and Link Invert Elevations Does SWMM 5 Use?
SWMM 5 uses the following Node information from the user:
· Node Invert Elevation,
· The Node Rim Elevation which is the Node Invert Elevation + the Maximum node depth
· The Ponded Area when the Ponded Area option is used
· The Surcharge Depth above the Node Rim Elevation
SWMM 5 uses the following link information from the user:
· The Link Upstream Offset Depth or Offset Elevation and
· The Link Downstream Offset Depth or Offset Elevation
· The Link Maximum Depth or Diameter
SWMM 5 calculates the following information internally:
· The Pipe Crown Elevation at the upstream and downstream link nodes. The Pipe Crown is the Pipe Diameter + Link Offsets
· The Node Highest Pipe Crown Elevation,
· The Surcharge Depth above the Rim Elevation if the Node has a Surcharge Pressure Depth at the Node during the simulation,
o If the Surcharge Depth is 0 then the program will either lose the flooded water or store the flooded water during the simulation
· The Flooded Depth above the Rim Elevation if the Node uses the Ponded Area Option
o You have to enter a Ponded Area for the node AND use the Global Allow Ponding Option
SWMM 5 Rules for Pipes
· The Pipe Invert Cannot be below either upstream or downstream node invert – the program will print a warning in the rpt file and set the offset to 0 internally,
· The Pipe Crown Cannot be above the Rim Elevation of the Node – the program will raise the Rim Elevation when this happens and print a warning in the rpt file.
The use of Offset Depth or Offset Elevation for the Link Offsets is based on the user choice at the bottom of the SWMM 5 GUI Map.
Or in the Tools/Preference/Operation dialog of InfoSWMM/H20MAP SWMM