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Sewer Storage not represented correctly

edited January 2019 in Water

I've been trying to account for sewer storage in one of my projects. As an example, I've added three sewer areas to my project, covering 188 ha (according to GIS). I've assigned a storage of 5 mm and a pump speed of 0 m3/s. When I select overlays -> add areas, I can see clearly that importing these areas went correctly. However, when I assess my mass balance, the sewer storage barely functions: it fills only with 1675 m3 (0,9 mm) of rainfall after a 60 mm storm event.

What could be wrong here?

  • I've set all sewer connection function values to 1.0 (to be able to assess the mass balance).
  • The sewer areas clearly cover all of the terrain that I'm assessing.
  • All sewer areas are checked as 'active in simulation'.
  • I've re-run and re-imported the files multiple times
  • The calculated value does not coincide with the expected storage in only one of the sewer areas.

Kind regards,


  • Hi Jacco,

    Can I have a look into your project to see what is happening with the sewer storage?
    Therefore I need to know the name of your project and you have to give Support access to your project. To do this, edit your project and click on the File button. Then you will see under Edit Rights Tygron Support. here you can give Support either read or write access (by default it is set on none).

    With kind regards,

    Tygron support team

  • Hi Godelief,

    The project is called Ulvenhout Nor 2, domainname is rhdhv. I've given rights to the support team.

    Kind regards,

  • Hi Jacco,

    Thank you for the access. I had a look into your project and noticed a few things.
    In your project there are no buildings, only roads, trees and gardens. Have you removed the buildings on purpose? Otherwise it could be that you generated the project with AHN3 and that it was not available for this specific area. Therefore no heights for buildings can be generated (it does not automatically fallback to AHN2). A solution to this would be to create the project again and not select AHN3.

    Because there are no buildings, only the roads are (by default) connected to the sewer. You can see what is connected by selecting the Base types result type in the Rainfall overlay wizard and refreshing the overlay. Now the Base Typology overlay shows the areas connected to the sewer (see also the attached images).

    To also connect other functions to the sewer, you can change the attribute Connected to Sewer in the Function values table (Step 3.3 in the wizard) and change the 0 (not connected) to 1(connected) for the desired functions. See also the attached image. For more information about the Function Values tabel, please see the Wiki:

    Since in your project only the roads are connected, there is only a small amount of sewer storage. To have the sewer storage functioning properly, I advise you to generate a new 3D model of the area and not select AHN3. Then you will have also buildings in your project. The buildings are by default connected to the sewer which results in a better repesentation of the sewer storage in the area.

    I hope this answers your question!

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    Tygron support team

  • Thanks for the clear answer and the feedback Godelief. I think the theory of the AHN3/AHN2 selection could be the right one; i most certainly did not remove buildings op purpose. Furthermore, in contrast to other projects,housed are not shown in a 3D-manner. In other projects this was the case.

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