Changing cross sections of a riverbed from a Lidar derived DEM.

[Anonymous]

Hi.

I want to investigate how different crossections of streets will affect urban flooding in 2d. I have a DEM- of the area and want to change the crossection of one street.

Do I need to manually change my DEM cell by cell in arcmap or is there a faster way to “manipulate” the tarrain in HECRAS

[Anonymous]

Heres what i do. I draw a reach and cross section in GIS (GeoRAS) the center line represents the terrain i want to manipulate. I import the geometry into HEC-RAS and change the cross sections to the shape i want. This does not matter if your cross section is a channel or a synthetic embankment or in your case a road elevation or geometry.

Once done editing the cross section go into RAS Mapper and right click on your geometry and click “Export Layer>>>Create Terrain Geo TIFF from cross sections and overbanks..” make the cell size small and it create a surface for your proposed road only. Then add new terrain and select the roadway terrain AND the original terrain. Make sure the roadway terrain is above the original terrain and click “create” you will see a manipulated surface without having to manually edit a terrain in GIS

[PaoloP]

I create a DEM using XS_Interpolator starting from cross sections of street and than I create the terrain in RAS Mapper using the original DEM and the one created starting from cross sections

PaoloP

[Anonymous]

Thank you!

I was trying hard to change the cross section in Arcmap, and did not realize that i could use Hec-georas
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[Author]

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