FloodPlain Mapping in 1D Channel

[Anonymous]

Hello guys

I have run a steady flow analysis for a river in 1d mode. The river has numerous small drops and hydraulic jumps. At the cross sections and flow profile of the analysis i can see the change of the water surface line due to the drops and jumps.
I now want to produce a floodplain map. I created the terrain from the cross sections and i added the depth layer based on the terrain in Ras mapper.
As i see at the floodplain map the water depth doesn’t include the transitions due to the jumps. Can i somehow show these in my floodplain results?

Regards
Paul

[Anonymous]

Hi,
I am sorry that i could not gave you the answr of your question because i am new to the hecras.
I write here becasue i see that you created a terrain from 1D geometry that you have. I also tried to create the terrain out of the 1D geometry but i couldnot get the terrain in a good shape. RAS Maapper has the option to get the terrain and its seems easy too but i dont know why i am not getting the terrain that i want ? if you have the ans to this please help me . Thanks

[Anonymous]

To make it more clear the floodplain mapping is not as accurate as the cross section and profile results along the river.

Paul

[Anonymous]

Hello Sudan
Right click at “GeometryData” in Ras Mapper –> Export Layer –> Create Geotiff from XS’s.
What is the problem with the terrain you create ?

Paul

[Anonymous]

its not like the terrain . I tried to use that terrain to run 2d simulation and the flow after simulation is like overland flow . I did the same procedure as you have mentioned but i coudnot figure what could be the mistake .

[Anonymous]

The terrain is like 3 square box with only three pixel vale.

[Anonymous]

What resolution did you choose for the terrain (raster cell size)? And what is the resolution for the 2d mesh you generated? Make sure you have the appropriate cell size for better convergence.

[Anonymous]

i choose 0.5 ft cell size for the terrain . its not even like a terrain . for 2d i use 0.5 ft too. i dont know whats wrong but it is giving me a lot of problem . seems easy but dont know where i made the mistake. could you provide me an example that you did to create a terran ?
thanks

[Anonymous]

You should better attach the project files in your topic to define the problem.

[Anonymous]

Has anyone compared the floodplain mapping depth with the cross section and flow profile results in a 1d dhannel?

[lkhoury]

I did. The depths and WSE values were the same and I have a pretty good jump in the channel. However at the outlet of a bridge and near levees the cross sections look different than the mapper. Even the XYZ is different and I was wondering myself which one is more accurate. It matters when you’re checking flood plains for developments.
Do you have any structures or levees? I am going to put the levee as a lateral structure and see if it solves the problem. If you find an answer I really want to know… hope that helped a little though..

[Anonymous]

I ‘m having both inaccurate WSE and Depth values at floodplain map in many cross sections even at those where there are no drops or abrupt transitions. I don’t have any structures or levees. I have designed the channel with some lids and even the sediment basin is simulated with detailed cross sections. The weird thing is that the terrain i created from the cross sections seems pretty accurate. Comparing the results with the floodplain mapping, the cross sections seem more reasonable.

[Author]

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