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How to set attribute array for dynamic breach height

I am using the Flooding Overlay in the Water Module to calculate flooding using a dynamic breach height. To set a dynamic breach height you can upload a CSV or set an attribute array in the attributes of the breach. The terrain height at the breach is around -1,5 m NAP.

I tried the CSV option to open the breach after (for example) 1 hour of calculation, the values are set in the CSV like this:

3600, 0

10800, -2

When calculated the breach immediately opens, supposed to opening after 1 hour. Adding a 0,0 to the start of the CSV is not working either.

I then tried to change the attribute Breach height into an attribute array using the following values

3600 0 10800 -2

This also opens the breach immediately.

How to set a attribute array for a dynamic breach height correctly?



  • Hi Harm,

    The way you have set the attribute array for a dynamic breach height, should be the correct way. Have you added the 0 0 values to the array as well? What I'm thinking is that maybe due to the amount of timeframes and the simulation time and based on the lineair interpolation of the breach height between 0 and -2, it looks as if the breach starts to flood immediately even though that is not the case. Because the first timeframe does not show the start of the simulation (see also: timeframes on the wiki )

    On the breach height page more documentation is added which explains how to set a dynamic breach height. You can try the example that is mentioned there in the Breach Growth project, which is available in all domains.

    If the assumption of the amount of timeframes is not correct for your project, I have to take a look in your project. Let me know if that is the case.

    Tygron support team

  • Hi Godelief,

    Thank you for adding more information on the dynamic breach height on the support wiki.

    When testing the dynamic breach height in the Breach Growth project the breach behaves as expected.

    When adding the dynamic breach attribute array to my project its behaviour is unexpected. The breach still opens in the first timestep. I have changed the number of timeframes and the amount of calculated hours. This does not effect the breach opening immediately.

    I think the next solution might have something to do with the breach type. This breach is located on a dike between the main water system and the polder. The breach should open after 1 hour allowing the main water system (which also receives water from inlets) to drain through the breach into the polder. Therefore I am not using a External input area of a Breach input area for this breach. I also want to calculate the lowering of the water levels in the main water system according to the breach flux. So only effectively lowering the terrain height at a certain location and time.

    Maybe I might be using the wrong assumptions for the breach for this model?

  • Hi Harm,

    In combination with an internal area it could also be the location of your breach area.

    It is best to draw the breach area not too close to the main water system (your internal area). The breach area does not have to cover the whole levee, but only the slope of the levee on the side of the area that is going to inundate (the polder). See also the image below, this breach area is only defined on the slope of the levee.

    Does this work in your project?

    Otherwise, can you send the name of your project to Support so I can take a look at it?

    Tygron support team

  • Hi Harm,

    Thank you for sending me the details of your project. I had a look into your project to see how your breach was defined.

    The issue in your project was the definition of the internal breach area. Since the breach is a local terrain height manipulation, basically the internal breach area should also be a small locally defined area, close to the breach where the terrain height is the same. In your project, the whole main water system was the internal area, Based on the amount of water that flows through the breach, water is also added back to the main water system (internal breach area) uniformly distributed, disregarding the height. If in the defined internal breach area the terrain level height varies, it can occur that too much water is added back to the main system on some shallower places. This was the case in your project and therefore the project flooded from the start.

    I have defined the internal breach area as follows in where the red part is your breach area and the lightblue part is the internal area. The internal area does not cover the whole width of the main water system, so the terrain height is the same value in the whole internal breach area.

    With for example the following breach height settings and a simulation time of an hour, the breach will flood only at the end of the simulation.

    I hope my explanation is clear and that you can reproduce the same in your project!

    The part about the internal area will be explained in more detail on the Wiki. I will post this link here when it is added.

    Tygron support team

  • Hi Godelief,

    Thanks for your answer. It explains a lot which I could not find on the Wiki (for now). It is probably a good idea to explain the internal area in more detail, but also how to draw a breach area on a levee (directly at the central page of the breach information, instead maybe at a tutorial page).

    The dynamic breach height is now working when I adjust the location of the breach and the internal area. But when looking into the flooding overlay it still seems the breach opens a little directly. The breach area and some grassland behind the breach already contain a small amount of flooding at timestep 1 (see the screenshot below). According to the topology overlay the breach is entirely active in timestep 1.

    The waterlevel in the measurement tool contradicts the visual flooding overlay. According to the measurement tool the breach seems to open after a few timeframes, when the breach is set to open, and immediately the water levels are raised significantly.

    Do you know why there is flooding visible near the breach and grassland in timestep 1?

    (I also used an inlet in the main water system to simulate a external inlet from another main water system. I used a dynamic lower threshold to do this, but I cannot find information at the Inlet Wiki page about this possibility. Maybe the Wiki can also be updated on the Inlet section, and other constructions which can use an dynamic attribute array.)

  • Hi Harm

    Thanks for your tips regarding the Wiki. We will use them to update the Wiki accordingly!

    I had again a look into your project. I noticed that you changed the breach area. The breach was now more on top of the levee, instead of how it was before, more on the slope of the levee on the side which is going to inundate. I removed a bit of the top of the breach area and now the breach does not start flooding anymore. I think the breach area was too close to the waterway and therefore it started flooding.

    This is how I defined the breach area:

    The information about the Inlet and its attributes can be found here on the Wiki:

    If something is missing, please let us know!

    Tygron support team

  • The wiki tutorials for defining a breach area are updated, see for more information:

    Breach with external area:

    Breach with an internal area:

    Tygron support team

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