SWMM5, InfoSWMM

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.

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

The height of a V-Notch weir is the Height Value in the SWMM 5 Weir Property Dialog (Figure 1) 

The Length in the Dialog for a V-Notch is the Top Width of Triangular Shaped V-Notch Weir. 

The slope of the sides of the V-Notch Weir is Square Root (1 + Top Width / Height / 2 * Top Width / Height / 2)

The full area is the Height * Height * Side Slope

The hydraulic radius is the Height / ( 2 * Height * Side Slope)

The two values Height and Length for a SWMM 5 V-Notch Weir determines the area, hydraulic radius and side slope of the weir.

Figure 1.   Parameters for a V-Notch Weir in SWMM 5

These are the estimates for both SWMM 5, InfoSWMM and ICM SWMM Hydrology, the low estimate is 0.2*SQRT(Area in Feet) and the High Estimate is 5*SQRT(Area in Feet), Figure 1.  You can use higher or lower numbers to calibrate to monitored data but these are just guidelines using the InfoSWMM Subcatchment Manager Width Tool (Figure 2).

Figure 1.  High and Low Estimates of the ICM Subcatchment Dimension for SWMM Hydrology or the SWMM 5 Subcatchment Width.

Figure 2  InfoSWMM Subcatchment Manager Width Estimator.