Peak flood depth arrival time

[Chris G-M]

Dear fellow HEC-RAS users,

Is it possible to produce an Arrival Time result map for the peak/max flood depth for each 2D cell? How the RAS Mapper input parameters are laid out, it seems only time to arrival for a discrete depth can be entered. If peak flood depth arrival time can’t be calculated within RAS Mapper, anyone have a work-around on how to do this using GIS tools?

Best regards,
Chris

[cameron]

You could get this from the hdf file. It lists the depth at each output interval so you could develop it in excel or other method by having it calculate the time of the max depth.

[Chris G-M]

Thanks for the response Cameron. Pulling depth-over-time from the HDF file has worked for now. Hopefully there will be a result map option for ‘Peak Flood Depth’ arrival time in a future RAS release.

[Karina Ramalho]

Hello Chris,

How did you do this?

[Chris G-M]

Hi Karina,

To access the HDF results I used HDFview software and then extracted individual peak flood depth arrival times using MATLAB. I ended up not creating a map of cell-by-cell peak flood depth arrival time. For my case it was sufficient to pick individual locations of interest, look up cell depth time-series from the HDF5 output, and then plot cell depth hydrographs to detemine peak flood arrival time.

Hope that helps,
-Chris

[Lonnie A]

Chris,
From the way I read of you method I don’t think you’d have to go the effort you did to get the information. In Mapper you can select a cell and have it plot the depth time series by right clicking on the location of interest with the depth layer turned on.

[Chris G-M]

Hi Lonnie,

You’re correct. If there are not many cells of interest then using RAS Mapper to plot individual depths-over-time would be sufficient. However, until HEC-RAS incorporates ‘max flood depth’ as an option for Arrival Time result maps, accessing cell depth info for many cells (e.g., entire 2D mesh) is straight forward using the HDF5 output.

For example, a rough max flood depth arrival time map could be produced via:
1) Export HDF5 cell depth results to Excel (or another program if output is too large)
2) Determine time to peak flood depth for each Cell ID
3) Join/associate the cell peak flood depth times to a shapefile of the mesh (GIS)

If someone has an easier or more RAS Mapper central approach, I’d be interested to hear your process.

Thanks,
Chris

[Anonymous]

Hi, chris
Is there any way to calculate the flood travel time from one location to another in 2d hecras model(with mesh only) ?

[Author]

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