Welcome to the RAS Solution Forums HEC-RAS Help Applying Manning’s n to 1D model in RAS Mapper

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  • #7343
    Anonymous
    Guest

    I’m editing an existing RAS model using Mapper in 5.0.6. I’ve successfully imported DEM and and a land use layer which has been converted to a raster. I can edit and create cross sections and update the XS geo based on the DEM, but cannot figure out how to update or assign n values to the XS, either in Mapper or in the Geometry editor. Is it possible to assign Manning’s n values to 1D cross sections using a shapefile in HEC-RAS?

    Thank you,

    Mike

    #12325
    Anonymous
    Guest

    No i do not believe you can do that. But the easiest way is to open the geometry data editor and at the top select “tables” “Manning’s n”

    Using that you can set multiple values at once. Takes seconds

    #12326
    Anonymous
    Guest

    Luis,

    Thank you but unfortunately the surface roughness of the area I’m modeling is complex and quite varied. I may have to go back to GeoRAS for this. If this is currently impossible, does anyone know when HEC plans on adding that functionality to Mapper? It seems like a significant speed bump if the goal is to move from model development from GeoRAS to Mapper.

    #12327
    gerardo
    Participant

    Tienes que calcular el “n manning” equivalente para el canal y las planicies de inundación de cada sección. Yo uso excel y la formula de la foto adjunta .

    You have to calculate the equivalent “n manning” for the channel and the floodplains of each section. I use excel and the equation of the attached photo

    #12328
    gerardo
    Participant
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