Note that RiverCAD does not have "plans" as HEC-RAS has where you can change between different geometry files. The problem is that we are operating within AutoCAD, and therefore limited to the confines of AutoCAD.
However, you can have multiple HEC-RAS models and corresponding geometries within the same AutoCAD drawing file. You can create a separate reach that is essentially the same as the previous model yet with the necessary changes to the geometry. You can define a new reach using Reach | Reach Manager | Add New Reach.
A quick way to duplicate your HEC-RAS model within AutoCAD (in order to make the necessary changes) is to export the current HEC-RAS model out (select Analysis | Export HEC-RAS Project). Then, re-import the same model you exported out, but place it in a new reach. RiverCAD will do that automatically for you when you import it (you do not need to define the new reach--it will do it for you).
If you have further questions, feel free to contact me or our technical support engineers.
Sincerely,
Chris Maeder, M.S., P.E.
Senior Technical Engineer
chris@bossintl.com