Russ:
Note that the contours that were created are splines--not polylines. While RiverCAD can handle lots of different entities, including 2D and 3D polylines, polyfaces, etc., we have never run into splines. So, I have asked our developers to look into adding support for splines, but it may take some time. In the mean while, you might want to see if the software that generated the splines can instead generate the contours as polylines.
Sincerely,
Chris E. Maeder, M.S., P.E.
Senior Technical Engineer
chris.maeder@bossintl.com