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HGL lower for larger rainfall event in CivilStorm

james Eason
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I have a Civil Storm stormwater outfall model setup to run the Implicit Dynamic Wave Solver. My areas are entered in with SCS CN data and my rainfall is entered as time-depth. I am running the 10-, 25-, 50-, and 100-year storm through the system and the main goal is to get a flood elevation at a low point in the system. There is an HGL increase in the HGL at the low point between the 10- and 25-year storm but not from the 25- to 50- or 100-year storm events. In fact the HGL actually decreases from 25- to 50- and from 50- to 100- The model volumes, volumes loss, continuity errors (0.2% max), and all of the other outputs for the individual scenarios seem to make sense. 

There is a diversion in the system where the main outfall splits, which this solver ignores but felt like I should at least mention it. The lowest two structures in the system are part of a tributary system and not the main outfall. These are the only structures in this part of the model that the HGl exceeds the rim elevation for the 10- and 25-year storms. In the 50- and 100-year storms there is another structure in the system that over tops. All of the structures that overtop have stage-storage ponding area above the rim as well. 

I am wondering if the structure in the main outfall that is overtopping in the bigger storms is giving me the issues that I am seeing in the model. I have double checked all of the background data and I don't see anything that looks wrong but I am not 100% sure what could be causing this. I also have a peak flow model in a separate file with the same system and it seems to be working and giving "logical" results. (I.e. the HGL increases with the increased rainfall). 

This is about the best I can describe the model and issues I am having. Any help would be greatly appreciated. I almost feel like it is something simple but I have exhausted everything I know to look for. 

Thanks in advance, 

James E. 

  • 0 Offline
    James,

    Regarding the "HGL" that you're comparing between storm events; is this the max HGL? If it's the HGL that you see right after running the model, you're likely looking at the time zero results. Be sure to graph the element (you can do this for multiple scenarios) or look at the "Max" result field.

    If this doesn't help, it would be useful to provide your CivilStorm version along with a copy of your model files (.STSW and .STSW.SQLITE, zipped, if using the latest version) and the locations/labels of interest. There are two options for sharing your model files on Communities. If you would like the files to be visible to other members, compress the files into a zip file and upload them as an attachment using the ‘Advanced Reply editor’ before posting. If your data is confidential, you can follow the instructions in the link below to send it to us via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley.

    communities.bentley.com/.../7079.be-communities-secure-file-upload


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • 0 Offline in reply to Jesse Dringoli
    Jesse, I was looking at the max HGL when I made my reference to how the system is behaving. I have uploaded the file per your direction. We have been looking at it internally and while intuition says that the model isn't behaving correctly, we haven't been able to find where the problem is. If you could take a look at the model and see if there is anything out of line, that would be very helpful.

    Thanks,
    James E.
  • 0 Offline in reply to james Eason
    James,
    We are working on your model.

    Terry Foster
    Technical Support
    Hydraulics and Hydrology product line
    Bentley Systems, Inc.


  • 0 Offline

    We took a look at your model in the latest build of CivilStorm (08.11.05.58) with the latest cumulative patch applied.

    Below is the data at a junction upstream fro the O-1 outfall.  As you can see the hydraulic grade increases between each scenario.

    This is a graph of the outfall O-1 in the different scenarios.  This is a slight difference between each scenario.  Is this what you are seeing?

    These values appear to be correct considering the flow and the size of the pipes.

    Terry Foster
    Technical Support
    Hydraulics and Hydrology product line
    Bentley Systems, Inc.


  • 0 Offline in reply to tlfoster56

    Terry, This is similar to what I am getting. My major concern was between structures EJB-2B and EDI-2D. Below is the 25-year storm HGL.

    The 50-year output for this outfall looks like this:

    This is the area that concerned me since the HGL actually lowered during the larger storms. If you step through this outfall in the 50- and 100-year storms it appears that it almost has two peaks. This one at time 12 hrs. and then another small peak about an hr later. Is this what the model is showing on your end? If the model seems valid on your end that makes me feel a little better about it but it doesn't follow conventional logic. 

    On a side note, Is there anyway to change the time step in the graphs (especially the engineering graphs) besides just getting as close to the peak as possible, hitting plan, and then hitting pause when the peak hits. I feel like there should be some easier way to do this. 

    Thanks for your help. 

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