6. CHAPTER 6: Reviewing Storm Drain Model Results
6.1. Introduction
After a FLO-2D storm drain model is complete, the results can be reviewed with both the FLO-2D QGIS program and the SWMM GUI. The QGIS displays the storm drain inflow and return flow hydrographs. A FLO-2D storm drain simulation will generate the following files in Table 22. A complete mapping lesson for an advanced FLO-2D Storm Drain model is available in the FLO-2D Documentation site (https://documentation.flo-2d.com/).
6.1.1. Step 1. Review the SUMMARY.OUT File
After a FLO-2D simulation is completed, the SUMMARY.OUT file can be reviewed with an ASCII text editor program. A FLO-2D model was successfully completed if the termination time and date is reported at the end of the SUMMARY.OUT:
Volume exchange and conservation between the surface water and storm drain is reported in the SUMMARY.OUT file as shown below.
Storm Drain Inflow: Reports the volume that represents inflow to the storm drain through the inlets and outfalls.
Storm Drain Outflow from Outfalls: Total volume of outfalls that discharge to the FLO-2D surface water and off the system.
Storm Drain Return Flow to Surface: Return flow to the surface water through the inlets as pressure flow.
6.1.2. Step 2. View the Surface Water Data and Results in QGIS
Open the project in the FLO-2D QGIS plug-in and go to the documentation folder to review the Storm drain advance lesson.
6.2. Viewing the Storm Drain Output in the SWMM GUI
The SWMM GUI creates the storm drain data input files and graphically displays the results. A FLO-2D storm drain simulation will generate output files that are compatible with the SWMM GUI. To view the output, first make sure that the following files are present in the project folder:
SWMM.ini
SWMM.inp
SWMM.rain
SWMM.RPT
SWMM.OUT
The SWMM.RPT file reports the storm drain output data in ASCII format and can be read with any ASCII editor. The SWMM.OUT file is a binary output file with results reported temporally and spatially that can be read by the SWMM GUI.
6.2.1. SWMM.ini
The storm drain results are not automatically loaded into the SWMM GUI. To load the results, navigate to the project folder directory and open the SWMM.ini file using an ASCII text editor. The user needs to set ‘Saved = 1” and “Current = 1” as highlighted in Figure 52.
Figure 52. SWMM.ini File with Required Data to View the Results in the SWMM GUI.
6.2.2. View the Storm Drain Results
Open the SWMM GUI and navigate to the project folder. Open the SWMM.inp file from the File >> Open menu. This will access the model output and enable the GUI to display the results as shown in Figure 53. The SWMM GUI has controls to label and color code the results in a variety of configurations.
Figure 53. Example Storm Drain Model in the SWMM GUI.
The SWMM GUI has some tools that can assist in the review of the storm drain output. The SWMM manual should be used referenced when using the SWMM GUI. The GUI environment is shown in Figure 54 consisting of a main menu, tool bars, study area, and working area. These attributes and some of the options are explained briefly.
6.2.3. File Menu
Open: Opens an existing project
Reopen: Opens recently used projects
Save: Saves the current project
Save As: Saves the project under a different name
Figure 54. SWMM GUI Environment.
6.2.7. Report Menu
Status: Displays a status report for the last simulation. The Bookmark feature enables quick review of the SWMM.RPT file sections (Figure 55).
Figure 55. Bookmark Interface that Facilitates a Review the SWMM.RPT File.
Graph: Command that displays simulation results in graphical form (Figure 56. Graph: Time Series).
Figure 56. Graph: Time Series.
Table: Displays simulation results in tabular form.
6.2.8. Tools Menu – Commands that Provide Control Detail
Program Preferences: Sets program preferences, such as font sizes, deletions, number of decimal places.
Map Control Display Options: Sets appearance options for the Map, such as object size, annotation, flow direction arrows, and background colors (Figure 57).
Figure 57. Map Options.
6.2.10. Study Area Map
This map is a working environment with a storm drain system.
6.2.11. Toolbars
Provide shortcuts to common operations and includes the standard toolbar.
6.2.12. Map Toolbar and Object Toolbar
Data/map browser provides access to all the data objects in a project and controls the mapping themes and time periods viewed on the study area map.
6.2.13. Status Bar
Auto-length: Indicates whether the automatic computation of conduit lengths is required. It is recommended that the auto-length be turned ‘off” if the data is imported from a GIS database.
Offsets: Indicate whether the positions of links above the invert of their connecting nodes are expressed as depth above the invert or as an offset elevation. The FLO-2D component is configured for the depth.
Flow units: English or metric. The previously entered data is not automatically adjusted for the unit system if the system is changed.
Zoom level: Zoom level percentage.
XY location: Mouse cursor coordinates.
6.2.14. Data Browser
The data browser has three sections (Figure 58).
A tree box that lists all the storm drain categories of data objects.
Edit buttons.
A list of individual objects in the selected category.
Figure 58. SWMM GUI Data Browser Panel.
6.2.15. Map Browser
The map browser consists of three panels that control the results display (Figure 59).
Themes Panel selects variables according to color on the map.
Time Period Panel indicates a specific output interval to display results on the map.
Animator Panel controls the animation of the temporal output and profile plots.
Figure 59. Map Browser, Time Output Interval to View Results and Animator Controls.
6.3. Model Checklist
The following checklist was prepared to review the storm drain data files:
Inlet location. All inlets must be inside the FLO-2D computation domain.
SWMM hydrology components are eliminated. If an existing SWMM model was ported to the FLO-2D model, all the hydrology features must be removed including subcatchments and rain gage features.
Pipe lengths. If pipe lengths are less than grid element width reset them to the grid element width.
Adverse pipe slope. Check adverse pipe slope for accuracy.
Inlet elevations. The inlet rim elevation should match the grid element elevation. Type 4 vertical inlets should go by the invert of the headwall. The invert of the headwall should match the grid element elevation. For type 4 inlets connected to channels, the channel invert should match the invert headwall opening. For Type 4 horizontal inlets, the grid element should match the rim elevation.
Type 4 - Defined by a Stage-Discharge Rating Table. Rating tables or generalized culvert equations must be assigned in the SWMMFLORT.DAT file.
Inlet geometry. Check the size and location.
Outfall discharge. For outfall discharge to the surface water, the outfall must have a ‘free’ condition and must be turned ‘on’ in the SWMMOUTF.DAT file.
Outfall location. Check the outfall location with respect to the grid/channel element and check the invert elevation with respect to floodplain/thalweg channel elevation.
Outfall to the channel. The outfall must be connected to the left bank grid element.
Tide gates for outfall nodes should be assigned in the SWMM.inp file.
Manholes. Check the assigned surcharge depth.
Storm drain model simulation completion. Check the SUMMARY.OUT file last line for the time stamp indicating that the model properly terminated.
SWMM.ini file. The SWMM.ini file should be modified to review the results.