[Luis Partida]

The HW and TW outputs are Maximum output values. Right click the structure and plot “stage and flow hydrographs” then follow the curve and determine the Q such that it exceeds the elevation of your spillway

[Luis Partida]

Your model is just unstable. Try adjusting your time step and adjusting your HTab parameters

[Luis Partida]

Do you see instability at 1D2D connections i.e. lateral structures? Each cell only gets one manning’s n value and it is based on the larger land cover area underneath the cell. What are your lateral structure weir coefficients? Have you increased the Lateral Structure flow stability factor from 1 to 3? Have you played with your computation time interval?

[Luis Partida]

Sorry bad advice, that isn’t an option in the SA2D conn editor only in lateral structures

[Luis Partida]

If you turn on particle tracing it may give you a better idea, but that is very odd. Is this in version 6.0?

The only explanation I can think of is look at your final manning’s value layer that RAS auto creates in RAS Mapper…expand your geometry and itll be under there. But even with this, it almost seems like a bug.

Do the cells ever get wet?

[Luis Partida]

Since you are modeling a wall, there is no need to extend your 2D area beyond that location. This is odd and I would look at a time by time basis to see when water gets beyond your wall. Is water even going through that culvert? It seems like its not. I believe you can also ignore the SA and just set your tailwater conditions to “out of system”

[Luis Partida]

It is best to get that output from the geometry data editor. You can click on the BC line and select “Plot stage and Hydrographs” you will get the same information

[Luis Partida]

Its not a direct setting it is just a way to tell the user to add volume at your discretion. You control how much volume a 1D SA has. Create your own table in the 1D SA editor

[Luis Partida]

Put a 1D storage area at the end of your mesh. Then, connect the 2D Mesh to the 1D storage area via a SA/2D Area Conn. In the Conn you can add your culvert. The 1D SA volume can just be set as infinite. Hope this helps

[Luis Partida]

I did get acceptable errors and now i would like to test it with 1D bridge results. But ok thanks for working back n forth with me.

I am going to refine the test so it isn’t as sloppy. Have a good one!

[Luis Partida]

I just found the work around with no Terrain mods…

So our limitation here and the problem is the cells, it is reading elevations that are blocking flow. So what I did was add a large refinement region around the bridge and its XS’s. From here i solved any associated cell errors and ran. But as you can imagine, if you need to span cells 300-ft so it ignores the high points, your transition back to your normal cell size would cause Courant variations depending on the original size of your model. Should i make a post on this? I have not seen anyone else solve this or bring up this issue yet

[Luis Partida]

It seems you are right. I cannot find a work around for this. This is disappointing, and the work around would literally have to be terrain modifications. 🙁

[Luis Partida]

I thought, the work around was to open your internal cross sections and copy and paste the US and DS cross sections into the US and DS internal bridge cross sections. RAS was not computing available flow area based on your internal Bridge cross section because it is most likely falling on the elevated roadway itself. BUT this did not work. Im going to investigate this further and get back to you

[Luis Partida]

Add pics of the structure editor as well as the geometry data editor with the terrain showing

[Luis Partida]

Sorry no, that’s what I meant, the Post Processing still does not contain Q. It still is always calculated on the fly each time the user requests the software to plot Q

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