Two options:
1. Use a corridor that daylights with an almost flat projection. Works OK
until you get into the bowtie areas.
3. Use a corridor with flat links that will extend out beyond the surface
interface. Create a surface from this, then run a volume analysis. Then draw
only the user defined contours and set only the 0 contour to show. Then
explode the volume and you have a polyline. Project that onto the EG and
you'll have your floodplain.
How's that RAS tool working out for you?
--
James Wedding, P.E.
Engineered Efficiency, Inc.
Civil 3D 2007
XP Tablet, SP2, 2GHz, 2G
www.eng-eff.com
www.civil3d.com