How to link a SWMM model to a 1D model using the map view

Flood Modeller provides functionality to enable you to dynamically link your 1D model with a SWMM model (EPA's Storm Water Management Model). If you have a geo-referenced 1D Model then it is possible to define these links within Flood Modeller and therefore visualise the locations of your SWMM node points. Your 1D model must be geo-referenced (or at least partially geo-referenced in the area where your links will be located). There are tools provided by Flood Modeller to apply geo-referencing to a 1D model and these methods are described elsewhere in this user guide.

The linking process does not provide any capability to build or edit SWMM models. It assumes that the SWMM model being linked has already been created in appropriate software, e.g. the EPA SWMM user interface. An existing SWMM model can be linked to 1D only via selected SWMM node types. These are:

The tool imposes no restrictions as to which 1D node you can create a SWMM connection at. However, care should be taken when selecting a suitable connection point as not all 1D node types represent a realistic linking option, e.g. on-line storage reservoirs are not compatible, use off-line instead.

The following section describes the step by step process for defining your SWMM model links:

  1. Use the Add GIS Data button (in GIS Data section of Home tab) to add your 1D model to the Flood Modeller viewport. The SWMM linking tool is compatible with a number of file types that can represent your model:
    • Flood Modeller model (‘.dat’) file – Flood Modeller will only read geo-referenced cross sections from this file

    • Flood Modeller cross section (‘.sec’) file – file containing only cross section node types

    • Flood Modeller geographic (‘.gxy’) file – file containing a single coordinate point for every node. This is actually loaded into Flood Modeller as an equivalent point shapefile.

    • Shapefile – can be a point, polyline or polygon shapefile that you have developed with one attribute field that represents the node names of your 1D model

  2. Use the Add GIS Data button (in GIS Data section of Home tab) to add any useful background map layers. These should be layers that will help locate particular SWMM node points, e.g. sewer outfalls. Background map layers can be raster grids (representing DEMs), aerial photos or map tiles (such as Ordnance Survey).

  3. Double click the Create 1D SWMM Link (isl) File option from the Toolbox:

  4. A new window will be displayed with options to select the 1D and the SWMM models you wish to build links between. First select your 1D model file from the dropdown box of (compatible) loaded files in your current map view. Then select the attribute field in your selected file that represents your 1D model node names.

  5. Next use the browse button provided to specify the SWMM model you want to link to. You need to select the ‘inp’ file of your SWMM model. After specifying this file the table in the interface will be automatically populated with a list of all SWMM node types compatible with linking to 1D.

  6. The tool is now ready to start defining links. Click the Start Linking button to begin this process. The button will change from green to red and the button text will change to Stop Linking. A snapping tool will then be activated on your map view, such that when you click close to a particular 1D node feature (represented by a point, line or polygon) the associated node label will be added to the selected row of table (in the 1D Node Name column). The selected row in the table will then automatically move to the next row where the1D Node Name field is empty. You can then continue to define the 1D node name for this row or click on a different row to select that one instead.

  7. For each defined link between 1D and SWMM you also need to define a connection type. This can be either a flow type link (signified with a “Q”) or a stage type link (signified with an “H”). The connection type defines which parameter data will be exchanged between the 1D and SWMM models at simulation run time. The connection type is defined by clicking on the dropdown box provided on each row of the table (in the Connection Type column). Select either the ‘Q’ or ‘H’ option (the ‘Q’ option is the default that will be set automatically for all rows when the SWMM model is first specified).

  8. A comment field is also provided on each row to enable you to add any additional information about any of your defined 1D SWMM links. First click on a particular comment field to enable you to add any text here.

  9. Repeat this 1D node selection process (as described in items 6 to 8 above) until all required 1D SWMM links are defined in the table. Note you can have rows with no 1D link defined or you can overwrite an already defined link (by re-selecting that row while linking). Then click the Stop Linking button (it will change back to green with text Start Linking). If you subsequently find that further links need to be defined or edited then you can click the Start Linking button again to carry out further changes to your link table.

  10. To utilise your defined links in a combined 1D SWMM model you need to save the contents of the links table to a text file. Click on the Save button on the 1D SWMM interface and specify a name and location for your file.

  11. You can now close the window. Your 1D SWMM link file is ready to be used in a simulation. Refer to the How to create a 1D-SWMM link page for an explanation on how incorporate this file into your 1D model simulation.


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