Hello,
I'm trying to determine the volume and depth of water on the surface of a catch basin inlet (CB-62), due to an underperforming pump at the outlet of a storm drain system.
I get a large continuity error and I can't figure out why. The error is likely due to the large "Total System Outflow Volume", which is inconsistent with the Total System Inflow Volume (which is correct as shown), but I don't
know how to troubleshoot this.
My initial approach to figure out the surface storage is the following:
When I run the model (ignoring the continuity error), looking at CB-62, at 15.95 hrs, I get a flow of 6.05 cfs, volume = 1.403 acft. These values reflect the hydrograph right before water begins to pond in CB-62.
The total volume of this hydrograph is 2.46 acft
The provided surface storage at CB-62 = 1.33 acft (this is represented in the "Surface Depth-Area Curve" in CB-62)
2.46-1.403= 1.06 acft < 1.33acft. This would suggest that the surface storage at CB-62 will is maintained within the defined surface storage limits.
However, after taking a closer look and graphing the CB-62, using Results (Extended Node)->"Depth (Flooding)" I see a depth beyond the 1.9-ft I had specified. Depth shown on the graph is 3.73-ft, suggesting water
ponds beyond the specified surface area. So, therefore, I'm not 100% sure my initial approach above is valid.
Any help would be very much appreciated. Files are attached.
Best,
-Mike
Storm Drain Hydraulics.stswpkg.zip
Hello Mike,
The following link has information on troubleshooting unstable results in a CivilStorm model: Troubleshooting unstable SewerGEMS and CivilStorm results using the implicit solver. This includes some recommendations related to the model itself that may help outside of what you have already tried. There are also some adjustment to the calculation options that can make.
I will note that I set the solver to be the Explicit (SWMM) solver with more stable results. I changed the solver in the calculation options, then changed the Routing Time Step to 1 second and the SWMM Output Increment to 0.1 hours.
If you are expecting overtopping and want to model the 2D surface flooding results, you can use the 2D Modeling option available in the latest version of CivilStorm. Information on this can be found here: 2D Modeling in SewerGEMS and CivilStorm. You would need to upgrade to access this.
Regards,
Scott