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drainage calculations

I have been asked to produce drainage calculations for my stormcad model. The model includes catchment areas so Q=CiA and catch basins horizontal layouts to calculate spread, capture, and bypass flows. Does anyone have a report, workflow, or idea on how I can create such a report? StormCAD Connect


  • Hello Brian,

    You can directly get the runoff from every catchment in StormCAD after analysis. If you need this information in a report you can generate the catchment report under Report > Gravity Tables. You can also simply copy the catchment flextable and paste into your report if that's what you are looking for.

    For catch-basins, you can get the spread, captured flow and bypassed flows by adding these columns in the catch-basin flextable. See the below article for customizing the flextables to getting necessary result data;

    Customizing FlexTables for viewing and reporting data

    You can also look at creating a custom report right out of StormCAD in which you can choose which tables, graphs, profiles can be included in your report. See this article which has details about this: Creating Custom Reports

    Hope this helps.


    Yashodhan Joshi

  • To add to Yashodhan's answer - since you're specifically looking for a report on catchment calculations (and maybe not the overall flow), I would recommend including fields in your Flextable or custom report like these (assuming you only have Rational flows from catchments):

    • Catchments
      • Catchment CA (this is the Rational C times the area)
      • Catchment Flow Time (the Tc)
      • Catchment Intensity (from the flow time and IDF curve)
      • Catchment Rational Flow (the resulting Q=CIA calculation - note this article on CFS vs acre-in/hr)
    • Catchbasins, manholes, conduits, channels
      • System CA (total upstream contributing area; C's times the areas)
      • System Flow Time (controlling flow time that is looked up on the IDF curve for the Q=CIA calculation - see this and this)
      • System Intensity (from the flow time and IDF curve)
      • System Rational Flow (the resulting Q=CIA calculation for contributing Rational flows)


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