GeoSWMM Model Builder

GeoSWMM allows a user to build a Stormwater network model in ArcGIS Pro and maintains all the model information in a project geodatabase. The model can be prepared in various ways such as:

1. Model Building by Browsing Input Feature Layers
2. Model Building from EPA SWMM Input data file (.inp)
3. Model Building in ArcGIS Pro map Using Standard GIS Editor Tab

Model Building by Browsing Input Feature Layers

It is very common for urban or municipal authorities to maintain stormwater network information in GIS. GeoSWMM provides an enhanced option for SWMM network model preparation when these GIS datasets are available. Rather than starting from the scratch, hydrologic models can be built from readily available network datasets. Most water or environment utilities information is managed in a GIS database.

If the stormwater network GIS data is available, user can browse to and add features via Import data > Import Layer option. User can populate the various GeoSWMM layers by selecting source data from the hard drive or by adding layers from the ArcGIS Pro Content pane (TOC). After adding each layer and completing the field mapping, clicking the import button allows the user to add the feature to a queue. once all the features are added to queue, click OK to write them to the GeoSWMM layers. In the following figures, the entire process has been shown step by step:

Click on Import Data  from the GeoSWMM tab. Or From the dropdown menu of Import Data select Import layer. 

An attribute mapping window will appear like following. Assign the property fields appropriately in this window. Then Click OK to accept the changes made and exit from the window. Note that you must assign the Name field. Other properties are optional. If not assigned, then the program-default values will be assigned automatically.

Click on Import button to add the external layer into the GeoSWMM project layer along with the mapped attributes/properties.

Follow steps 2-3 similarly for objects- Rain Gages, Junctions, Outfalls and Conduits.  You can map the layer attributes in any order. While mapping subcatchment and conduit properties, you can assign custom area and length entries respectively, by specifying User Defined Area and User Defined Length fields. If these fields are not specified, GeoSWMM will automatically calculate the subcatchment areas and conduit lengths using the ArcGIS Pro map projection information.

Click on OK button to complete the importing process. The model network is already developed. After the mapping is complete, click on the Save () button on GeoSWMM tab. The project will be saved and show you a notification message like the following figure. Click OK to accept.

Notice that the geodatabase shows its layers with program-default symbology. However, you can also use the object symbology properties from the supplied layer (.lyrx) files. Uncheck/ remove the shape files in the table of contents. Now the ArcGIS Pro map window will display only the model geodatabase features. The Model Object Panel also shows a list of objects under each network item. Model network building is complete. Now label the object feature classes as shown below.

During property mapping, it is not essential to assign all of the parameters from the data layer fields except for the Name field, which is the unique identifier for any visual object in SWMM model.

Model Building from EPA SWMM Input Data File (.inp)

GeoSWMM allows users to seamlessly import existing stormwater models created in EPA SWMM by reading input (*.inp) files. This feature enables efficient migration of non-GIS models into the ArcGIS Pro environment, while preserving all hydraulic and hydrologic components. During import, the EPA SWMM model is automatically converted into spatial GIS data, allowing users to visualize, edit, and enhance the model in a fully integrated GIS framework.

Before You Begin: Coordinate System Requirements

Since GeoSWMM is a GIS-based platform, importing an EPA SWMM input file will create spatial data layers for all model objects (subcatchments, nodes, links, etc.). To ensure proper alignment on the map, it is essential that:

• The .inp file contains valid coordinates for all model elements.
• These coordinates correspond to a known projected coordinate system.
• The GeoSWMM Project is created using the same coordinate system as the input file.

Tip: If coordinate systems are not consistent, the imported model may appear in the wrong location or show spatial distortions.

Importing an EPA SWMM Input File During Project Setup

When a new GeoSWMM Project is created, GeoSWMM prompts you to set up a model:

If the .inp file is imported successfully, GeoSWMM will display a confirmation message and the model objects will appear in the map. It is recommended that you save the GeoSWMM Project immediately after a successful import.

Importing after Initial Project Creation

If you do not import the .inp file during the initial project setup, you can still import it later:

Navigate to Project → Import SWMM Input File,

or click “Import Data” from the menu and select “Import SWMM Input File”.

Follow the same steps (3 and 4) from the previous section.

Model Building in Arcgis Pro Map Using Standard Gis Editor Tab

Another way to prepare a SWMM network model in GeoSWMM is by utilizing the ArcGIS Pro Edit Section. When the user doesn't have any model information, but it can be manually generated from the raw field data or GIS maps, the model can be developed using the Edit Section. Under this condition, the user may start creating or editing features in the project geodatabase layers and then populates the input data fields. After all of the features are successfully digitized and assigned with suitable attributes, the model can be generated by clicking on the Reload () button on the GeoSWMM tab. Significant effort might be required for digitizing all the elements and populating the object properties with this approach; however, when the model is small or schematic, applying this approach could be useful for a SWMM user.