EPA SWMM to TUFLOW

Introduction

TUFLOW has supported 1D/2D dynamic coupling since its initial 2D solver development in 1989. Traditionally, 1D linking and associated modeling has been applied using the TUFLOW 1D (ESTRY) solver. New in the 2023-03-AD Release, TUFLOW's 1D linking and solver options have been expanded to support the EPA Storm Water Management Model (referred to herein as SWMM).

As a result of the 1D SWMM inclusion within TUFLOW, modellers working with SWMM files now have a variety of options available:

1. Use SWMM, coupled directly to TUFLOW.
2. Conversion of SWMM 1D geometry to a TUFLOW compatible format for use by the TUFLOW 1D (ESTRY) solver.

SWMM inclusion in TUFLOW (2023-03-AD or newer)

If you wish to model SWMM coupled dynamically to TUFLOW 2D, please refer to the TUFLOW SWMM Tutorials and Chapter 4 of the 2023-03 Release Notes. Step by step model build examples are provided for the following topics:

• TUFLOW SWMM Module 1 - 1D SWMM Culverts
• TUFLOW SWMM Module 2 - 1D SWMM Pipe Network / 2D TUFLOW Direct Rainfall Hydrology
• TUFLOW SWMM Module 3 - 1D SWMM Pipe Network / 1D SWMM Urban Hydrology
• TUFLOW SWMM Module 4 - 1D SWMM Pipe Network / 1D SWMM Urban Hydrology: Executing multiple different event simulations from a single model control file.

Conversion of SWMM to TUFLOW 1D (ESTRY)

As an alternative to direct coupling of SWMM with TUFLOW, a free utility tool is also available to assist with the conversion of SWMM inp files into a TUFLOW compatible format for simulation using TUFLOW 1D (ESTRY). The SWMM_to_TUFLOW utility is available for download from the TUFLOW website.

The SWMM_to_TUFLOW utility automates the conversion of SWMM 1D model geometry for culverts, pipes and open channels into a TUFLOW 1D (ESTRY) compatible GIS and tabular format.

Note: TUFLOW 1D does not include an inbuilt hydrology engine. As such, SWMM hydrology and boundary condition information is not processed by this utility. If SWMM hydrology or boundary condition information is important for your model build, please use direct coupling of SWMM with TUFLOW.

SWMM_to_TUFLOW Utility Execution

The following steps outline how to use the SWMM to TUFLOW utility.

1. Save the swmm_to_gis_w64.exe to the same folder as the SWMM file (.inp).
2. The utility requires GIS projection information to correctly translate the spatial information contained within the SWMM file (.inp) to either MapInfo *mif/*mid or ESRI/QGIS *.shp format. This is done by including a Projection file in the working directory. Create one of the following files, saved to the same folder location as the SWMM file (.inp).
   • *mif format input requirement: Projection.mif
   • *shp format input requirement: Projection.prj

   The following error message will be produced if projection information is not provided:

   ERROR - A Header.prj or Projection.prj file does not exist in folder
   

3. Create a batch file (*.bat) in the same folder as the SWMM file (.inp). Depending on the GIS output format you desire, use either of the following syntax in the batch file:
   • *mif/*mid format output desired: swmm_to_GIS.exe -mif SWMM.inp
   • *shp format output desired: swmm_to_GIS.exe -shp SWMM.inp
4. Double left mouse click the created batch file from Windows Explorer to execute the utility.
5. If the utility does not execute cleanly for the entire dataset a Warning or Check message will be written to the DOS Command Prompt and the processing will be paused. Press "enter" to continue, and when the utility is complete, open the result files to manually inspect and address the feature that triggered the warning / check pause.

Utility Output

Depending on the features included in the SWMM file (.inp) the utility may create the following TUFLOW 1D input files:

Utility Output	MapInfo (mif/mid)	ESRI / QGIS (shp)
1D Invert Information	1d_nwk_...junctions.mif / mid	1d_nwk_...junctions_P.shp
1D Geometry Details (link type and size)	1d_nwk_...inp.mif / mid	1d_nwk_...inp_L.shp
1D Open Channel Cross-section Locations	XS Folder 1d_xs_...transects.mif	XS Folder 1d_xs_...transects_L.shp
1D Irregular Culvert Cross-section Locations	XS Folder 1d_hw_...inp.shp	XS Folder 1d_hw_...inp_L.shp
1D Open Channel Cross-section Data	.csv files contained within the XS Folder
1D Irregular Culvert Cross-section Data	.csv files contained within the XS Folder

Example TUFLOW 1D Commands associated with the output files are:

Read GIS Network == gis\1d_nwk_Example.inp_junctions_P.shp ! 1D invert information
Read GIS Network == gis\1d_nwk_Example.inp_L.shp ! 1D geometry details (link type and size)
Read GIS Table Links == xs\1d_xs_Example.inp_transects_L.shp ! 1D cross-section location and csv data cross references
Read GIS Table Links == xs\1d_hw_Example.inp_transects_L.shp ! 1D irregular culvert cross-section location and csv data cross references

Limitations

• SWMM open channel geometry may include both the channel and adjacent floodplain within the cross-section information. If the intention is to link the 1D to TUFLOW 2D, with 2D representing the floodplain, manual update of the cross-section information to limit the extent of the open channel section will be needed. The cross-section extent is displayed spatially in the GIS cross-section output. Edit the associated csv out file to modify the cross-section properties used in the modelling.
• SWMM includes a larger range of inbuilt culvert geometry types than TUFLOW 1D. TUFLOW 1D primarily supports Circular (C) and Rectangular (R) as hardcoded culvert / pipe geometries. All others SWMM culvert types are converted to TUFLOW 1D Irregular (I) culverts, with an associated Height vs Width 1D cross-section to define the culvert geometry.
• SWMM includes a variety of inbuilt pipe network inlet geometries. This information is not processed by the utility. It is the modellers responsibility to manually create depth / flow relationship information for the pit inlet database if using TUFLOW 1D. If you wish to use the inbuilt SWMM pipe network inlet geometries directly, please use direct coupling of SWMM with TUFLOW. Refer to TUFLOW SWMM Tutorial Module 2 and 3
• TUFLOW 1D does not include an inbuilt hydrology engine. As such, SWMM hydrology and boundary condition information is not processed by this utility. If SWMM hydrology or boundary condition information is important for your model build, please use direct coupling of SWMM with TUFLOW.