RiverCAD allows you to export your model to HEC-RAS and then you can run the unsteady flow computations in HEC-RAS. Then, RiverCAD can read to unsteady flow output file and can map the inundation extents of the peak flow on the topo map.
Please let me know if you need further detail on how to do this.
Sincerely,
Chris E. Maeder, M.S., P.E.
Senior Technical Engineer
chris.maeder@bossintl.com