Draw 3d polylines on DEM based on elevation

[makdak]

Hello, I want to draw 3d polylines on a DEM that represent flood levels. I have a river centerline, some cross section lines, an excel table with water surface elevation on each of these cross sections and a DEM. What I am looking for is for a way to identify the 2 points where each cross section crosses the DEM at the water surface elevation on either side of the river centerline and then connect those points so that I get two 3d polylines representing flood levels. Any ideas? Thank you.

[rl_jackson]

I taking it that you have a DEM of the River, and you have created a surface from that. Assuming you have your EG surface, you which has the banks of the river, you can create user contours at the different water surface elevations, and extract the resulting user contours as 3d polylines.

[AllenJessup]

If I understand correctly. Create a water elevation Surface. Then use the water elevation Surface and the existing Surface to create a Volume Surface. Show the Volume Surface as Contours and extract the polylines from the 0 contour.

[essam-salah]

Hi @makdak 

assuming that you have a Water surface and the river it self as a surface and you want to get the intersection between the two surfaces as 3d polyline, you can use MinDistBetweenSurfaces Civil3d Command to get the two polylines.

[essam-salah]

@makdak 

regarding how to create the river surface, 

since you have the cross section of the river and the center line you can create a corridor out of them using the center line as alignment and the cross section lines as assembly and create design profile from the excel sheet data.

[tboehler]

Are you using data from HEC-RAS?  If so and you have Civil 3D you can export the data from HEC-RAS straight into Civil 3D.  It's been a while but I remember it works well (enough).

[ChicagoLooper]

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@makdak wrote:

<<...Hello, I want to draw 3d polylines on a DEM that represent flood levels. .....Any ideas?>>

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I don't think you want to draw 3D polylines on a DEM, you want to draw a polyline on a TIN surface. What does this mean? It means you must use the DEM to create a surface first, then you can perform your analysis.

Is it possible to share your DEM? Or porvide the web site where the DEM came from.  

[Pointdump]

Hi John,
>>>This Video<<< from Jeff Bartels might get you close to what you want.
Dave