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How are Flooded Time, Surcharged Time and Flooded Volume Calculated in SWMM 5?

The time, volume and flooded rate shown in the SWMM 5 Report File Node Flooding Summary (Figure 2) are calculated as follows (Figure 1):

For All Nodes NOT Outfalls ( this includes Junctions, Storage Nodes, Dividers)

If the New Volume is greater than the Full Volume of the or there is Overflow then at each time step the Time Flooded is increased

If the New Volume is greater than the Full Volume of the or there is Overflow then at each time step the Volume Flooded is increased by the Overflow * Time Step

If the New Volume is greater than the Full Volume of the or there is Overflow AND Surface Ponding is Used then the Ponded Volume is New Volume – Full Volume

If the Node Depth Plus the Node Invert Elevation is above the Node Crown Elevation then at each time step the time surcharged is increased. Figure 1.  Levels of Surcharged and Flooding in SWMM 5. Figure 2.  SWMM 5 Node Flooding Summary

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• How are Flooded Time, Surcharged Time and Flooded Volume Calculated in InfoSWMM and H2OMAP SWMM?

The time, volume and flooded rate shown in the InfoSWMM and H2OMAP SWMM Report File Node Flooding Summary (Figure 2) are calculated as follows (Figure 1):

For All Nodes NOT Outfalls ( this includes Junctions, Storage Nodes, Dividers)

If the New Volume is greater than the Full Volume of the or there is Overflow then at each time step the Time Flooded is increased

If the New Volume is greater than the Full Volume of the or there is Overflow then at each time step the Volume Flooded is increased by the Overflow * Time Step

If the New Volume is greater than the Full Volume of the or there is Overflow AND Surface Ponding is Used then the Ponded Volume is New Volume – Full Volume

If the Node Depth Plus the Node Invert Elevation is above the Node Crown Elevation then at each time step the time surcharged is increased.   The InfoSWMM and H2OMAP SWMM Map Display variables should be FLOOD_VOLM for the No Surface Ponding option (Figure 3) and PONDED_VOL if you are using the Global Surface Ponding Option (Figure 4). Figure 1.  Levels of Surcharged and Flooding in SWMM 5. Figure 2.  SWMM 5 Node Flooding Summary or the InfoSWMM and H2OMAP SWMM HTML Report file. Figure 3.  The Map Display of the Node Flooding using the No Surface Ponding Option should use the Map Display Variable FLOOD_VOLM Figure 4.  The Map Display of the Node Flooding using the Surface Ponding Option should use the Map Display Variable PONDED_VOL which shows the Maximum Stored Pond Volume.

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