Dam break analysis – Output Hydrograph explanation

[igorce]

Hallo,
On the pictures below you can see the peak of the hydrograph for different location in flood area. The distance between this two cross section is 7000m. First cross section have peak 7363 cms, and the second cross section have 4916 cms.
Is this logical, what is your experience, it is more logical to get low results after that distance?
How can i explain the sustainability of such a large peak flow at this distance. From 7363 cms only to 4916 cms ?

[cameron]

That can be normal. There is a lot of attenuation in peaks as you go downstream.

If you took a hydrograph plot inside of the canyon before it spreads out, the peak would not have attenuated that much as it is confined. Once it gets to the open area it just spreads out and slows down.

[igorce]

Thank you cameron.
I have additional simple short question.
Why the software give us output hydrographs with negative values?

[Chris G-M]

Orientation of your profile line relative to the direction of flow will determine if estimated discharge is negative or positive. Profile lines drawn left-to-right, looking downstream from the direction of flow will yield positive outflow estimates. Your profile line in the screenshot is drawn from right-to-left.

[Anonymous]

Just something else to add. 7000m between 2 cross sections is too far especially in an unsteady model (1D or 2D). To better understand oddd results it is best to place intermediate cross sections at much lower intervals. Then the results can be evaluated for their validity

[igorce]

I appreciate your support. Thank you very much

[Author]

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