How to Calculate the Freeboard of a Node in InfoSWMM/H2OMAP SWMM from the Model Results

The freeboard for a node in InfoSWMM/H2OMAP SWMM can be calculated with a 5 step process:

1. Copy the Node Rim Elevations from the DB Tables for Junctions to Excel, you need to use the Preference Option Store Absolute Junction Rim to have the absolute elevation and not just the maximum depth of the node (Figure 1).

Figure 1. Copy the Output Report Manager Tables to Excel

2. Run the model and then copy the Maximum HGL from the Junction Summary Output Report Manager table to Excel (Figure 2).

Figure 2. Copy the Maximum HGL from the Junction Summary Output Report Manager table to Excel.

3. Calculate the Freeboard in Excel as the Rim Elevation minus the Maximum HGL in Excel, this will be either positive or negative depending on whether you are using the surface ponding option. Positive if there is Freeboard and negative if there is flooding (Figure 3).

Figure 3. Calculate the Freeboard in Excel as the Rim Elevation minus the Maximum HGL.

4. Create a new column called Freeboard in the Junction Information DB Table and paste the Freeboard from Excel. You will first have to make a new column called Freeboard and specify the type of number(Figures 4 and 5).

Figure 4. Make a Freeboard Column in the Node Information Table.

Figure 5. Map Displays or Map Queries using the new Freeboard information column.

5. You will now be able to perform Map Displays or Map Queries using the new Freeboard information column (Figure 6).

Figure 6. Create a new column called Freeboard in the Junction Information DB Table and paste the Freeboard from Excel.