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Stormwater Drainage Subcatchment characteristic width & Slope

Greetings,

We are working on Urban drainage design using SewerGEMS latest version of 10.03.04.53 with Explicit solver & EPASWMM runoff method.
In which the catchment characteristic width & slope are inputs to the model (shown in below screenshot). Is there any possibility to calculate the Catchment characteristic width & slope in SewerGEMS.
Could you please explain about these inputs and how it facilitates the runoff flow & volume.

Regards
Ganesh Bala S

  • Hello Ganesh, 

    EPA-SWMM runoff method is taken from EPA-SWMM so you can find more information on that method in SWMM hydrology reference manual, which you can download here;

    Storm Water Management Model (SWMM)

    Additionally, please see the following article for more information. It is focused around differences between the unit hydrograph and SWMM runoff methods, but there are some links included that you may find useful.

    Results Different between Unit Hydrograph and EPA-SWMM Runoff Methods

    For non-zero values of these fields error will be generated. 

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • To add to Sushma's reply - generally speaking you can see a short description of input fields by clicking on them in the Property grid and looking at the bottom. See: Where can I find the definition of a property?

    As Sushma mentioned, these particular inputs are based on the standard EPA-SWMM runoff method and are needed in order to compute the runoff hydrograph. You can see more information specifically about SWMM runoff in chapter 3 of the Hydrology manual (download found on this page)

    If you're still not sure how to determine these parameters, you may want to consider if this is the right runoff method for you. Your local reviewer may require a certain runoff method, and you may find that the Unit Hydrograph method for example may be better, especially if it's required parameters and storm information are more readily available to you.


    Regards,

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

  • Hi Sushma,

    Thank you for the above information, we will check with SWMM manuals.

    Could you please suggest whether it is possible to generate these parameters (characteristic width & slope) in SewerGEMS software?

    Regards

    Ganesh Bala S

    Regards

    Ganesh Bala S

    Design Engineer

    Khatib&Alami Engineering Consultants Pvt. Ltd.

  • Currently the Characteristic Width and Slope fields for catchments when using the EPA-SWMM runoff method must be entered by the user or imported via ModelBuilder from an external data source. 


    Regards,

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

    Answer Verified By: GANESH BALA S