Create cross sections in HEC-RAS to modify terrain on RAS Mapper

[albern]

Hi guys

I’m new to using HEC-RAS and I am working on a flood hazard mapping project in Canada using HEC-RAS 2D.

I think this is quite beginner level and obvious to most of you but I can’t find any information on the forum or web so I try here 🙂

I want to modify my terrain file in RAS MAPPER (adjusting my river depth, clearing out the bridges blocking the current for example). I read in the User Manual that it was possible with the XS interpolation surface tool but in order to do that, I need to create some cross sections.

So the question is :

How do you create your cross sections in order to modify your terrain on RAS MAPPER ?

– Do you use an imported geometry files from HEC-GeoRAS ? (I tried that but the geometry layers are in a different location than my terrain…) Maybe I’m doing it wrong but can’t find where… (the layers in ArcMap are in the same coordinate system as the terrain file in RAS Mapper…)

– Do you draw them directly on the geometry data window ? Using the measure distance tool from RAS-Mapper to define the geometry of each cross section by example… This looks quite time-consuming and not precise compared to the first proposition (position of each cross section on the river line, cross section not necessary perpendicular to it etc.)

I’m quite stuck at this point and don’t know where to look for an answer. Your help would be very much welcome!

Thanks in advance

Alex

[Lonnie A]

Albern,

These two post by Chris G. may be of help to you.

http://hecrasmodel.blogspot.com/2015/06/lifting-terrain-in-hec-ras-50.html

http://hecrasmodel.blogspot.com/2014/12/including-channel-bathymetry-into-your.html

You will create geometry for the terrain edits in the geometry editor typically.

[albern]

Thanks for your answer @Lonnie A !

I managed to find a solution to my problem (it was the unit conversion ).

For those who are struggling in this process here’s what I did :

– First create your geometry in HEC geo RAS, so river, bank, flow path and XSCutLines layer etc.
Do like you were meaning do compute 1D analysis in HEC-RAS

– Export your RAS Data,

– Open your HEC RAS document and import the GIS geometry file, be careful of the unit !! (That was my problem…) Otherwise your imported geometry will be in a completely different place in the coordinate system

– On RAS Mapper import your terrain file if it’s not already done

– Turn on the geometries layer and do the process indicated in @Lonnie A’s second link

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