I have the z-values of the contours (physical contours) of a watershed in AutoCAD civil, but I may use them in ArcGIS 10.2 and I have already created a DEM. I need to extract the z-values for the stream, in order to create the AgreeDem and to continue with the fill and flow accumulation process in ArcGIS.
An option would be to take your stream network and convert it to a 3D feature using the 3D Analyst in ArcMap. The Tool you are looking for is:
This is located under - 3D Analyst -> Functional Surface -> Interpolate Shape Here is the help file if you want to read further into how the tool works: ESRI - Interpolate Shape
Select the DEM as your Input Surface and your 2D River Layer as the Input Feature Class.
This should be what you need to run the AGREE_DEM.