6.4 SWMM Outputs

Model outputs are written by both SWMM and TUFLOW, which can be used to visualize model results. SWMM writes a report file (rpt) and an output file (out) in the TUFLOW results folder with the simulation prefix followed by “_swmm.” The report file can be viewed with a text editor. The output file can be viewed in EPA SWMM or 3rd party tools that support this format, such as PySWMM.

TUFLOW-SWMM models also output a GeoPackage time-series output file. The file is written to the “plot” subfolder within the results folder and ends with “_ts.gpkg.” This file is referenced in the TUFLOW tpc file (see Section 15.2.1) which includes the other time-series outputs such as 1D ESTRY and 2D PO. The QGIS TUFLOW Viewer can read the SWMM results using the Load Results - Time series option from the File menu and selecting the tpc (load all time-series results) or GPKG time-series file (only load SWMM results). When the SWMM GPKG time-series file is loaded, point and line layers will be loaded, representing the node and channel results. The layer symbology can be modified to dynamically represent the model result magnitude for the current QGIS time. Profiles can be also be generated for the 1D network. Animations can be created from these results (in combination with 2D results if desired). These layers can also be used to select channels or nodes to display time series results in the TUFLOW Viewer plot windows, and can be combined with ESTRY or PO outputs. Documentation for the QGIS TUFLOW Plugin and TUFLOW Viewer are available in the TUFLOW Wiki.

The GeoPackage time-series file contains all of the SWMM output for nodes and links (polylines). For nodes this includes, “Depth”, “Water Level”, and more. For Conduits this includes, “Flow”, “Channel Depth”, “Velocity”, “Channel Capacity” and more. Descriptions of these datasets are in the SWMM documentation.

In addition to the SWMM output variables, TUFLOW writes additional node datasets as described below:

  • Cumulative Volume from 2D - the total volume (m^3 or ft^3) from the 2D domain into the node (negative values indicate surcharging).

  • Flow from 2D - The discharge (m^3/s or ft^3/s) from the 2D domain into the node for each output time (negative values indicate surcharging).

  • Inlet Inflow Duration - The duration (hours) that there is positive flow from the 2D domain to the node through an inlet. Non inlet nodes are not represented.

  • Inlet Surcharge Duration - The duration (hours) that there is surcharging (negative flow reported in Flow from 2D) from the node into the 2D domain for nodes connected to inlets. Non inlet nodes are not represented.

  • Inlet OnGrade Duration Percent (only written if inlets with Automatic placement exist) - The cumulative percentage that an inlet functions as on-grade compared to on-sag (TUFLOW-SWMM applies the higher value).