Floodplain Mapping not so satisfying results

[Ondřej]

Hello everyone,
I am working on estimating flood area on Smolnický river in Czech Republic. Everything went smooth, but I am not satisfied with resulting flood area. At some area this kind of error is occuring – kind of gaps between two cross sections. I used leeve and innefective area on the left overbank, where the flooding occuring, but it looks this kind of error is causing leeve.

Q10 –

Q20 –

Thank you for your help.

[gerar200]

– deleted –

[Ondřej]

If I insert interpolated XS between the measured cross sections the flooded area remains same, in some cases the problem is worse.

EDIT: The cross sections are interpolated by 5 meters.
Q-5

Q-20

[Anonymous]

The issue is not the DS xsections it is the upstream xsections. The orientation of them looks very off. Provide an image of the model zoomed out more to see the upstream cross sections as well as the other cross sections where this problem is assumed.

When running a !d simulation and correlating this to a graphical output in the inundation modeling, the modeler must understand that the image displayed is only as good as its mathematical input. You can orient a cross section any way you want as long is its left to right looking downstream, the results are still only as good as the numerical input. Its solving equations based on your numerical input not the orientation of your cross section in plan view

[Ondřej]

I removed all the leeves from the model and everything looks good without that error. I also removed the interpolated XS, beucause they caused even more mess. n my model now the overbank flooding occuring, which is not what I want, in some cases it is ok. But I still wondering if is there a way to make the leeves work without described problem above.

[Anonymous]

Its your cross section orientation upstream of the problem area that is associated with the left, channel and right ds reach lengths. Cross sections must be cut perpendicular to the contour as well as the stream. Thhis means you need cross sections with odd shapes and angles and that is ok. The way you have cross sections in the middle of that model, with some a high angle and the ones downstream being near straight , is causing your issue

[Author]

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