Developing a HEC-RAS model in 2D only

[Dr. Khan]

Hi All,
I am trying to model a floodplain that has two main rivers flowing through it. Currently I am doing it as 1D/2D model but I am keen to do it in 2D only as well. Can any one please share experience of modelling rivers in 2D only and comparing it with 1D/2D runs? Do we get the same conveyance in the channels when modeled in 2D? Please share any key considerations.
A snapshot of the floodplain and rivers is given below:

[Anonymous]

Full 2D will be a much faster set up and will, in my opinion , convey the final results in a much clearer product….if set up right.

Pointers:
1)Have a mannings n shapefile representing the terrain, if it varies make sure the shapefile varies and has a generated cell size similar to your computational mesh, only 1 n value is assigned to each cell

2) breaklines are imperative. They must represent high points and low points. For the model shown in your screen shot banklines and chanel CL may work just fine.

3) Output results are only quickly shown where you tell RAS to compute (ie inline weirs at the elevation of the underlying terrain in order to obtain a flow. If you want full output at each cross section you will have to draw profile lines in ras mapper and once the model is complete have it plot water data you need. I have found this to take the same time to run model. I.e. model runs in 30 minutes, producing a hydrograph will take another 30 minutes. But it only needs to compute once. Im not a robot

[Author]

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