There are several ways you can do this.
1. You can create a template cross section that you want to use for the existing channel, as sort of a channel cut, and have RiverCAD merge this into the current cross section. You need to set your template cross section file up as an ASCII text file. This is documented in the User Manual as well as several places in this forums. You can then import this file into the current cross section by selecting Input | Ground Geometry | Edit Geometry. From the Edit Geometry dialog, click on the Import button. Select your ASCII text file. You can then use the controls in the Merge Geometry dialog that is displayed to locate where the channel cut is supposed to go.
While this method takes the most to setup (does not take more than 5 to 10 minutes), it is probably the most effective if you have to do a lot of cross sections.
2. You can manually adjust the geometry. Select Input | Ground Geometry | Edit Geometry. From the Edit Geometry, click on the New button. You can the graphically "draw" the revision on the cross section.
3. You can use the Channel Improvement / Channel Modification feature in RiverCAD to revise the cross section. However, I don't exactly like this feature as much as the others.
4. You can export your RiverCAD model out to HEC-RAS, and you can modify the geometry within HEC-RAS' channel modification feature and then reimport the revised ground geometry back into RiverCAD. I have used this feature quite often with good results.
Sincerely,
Chris E. Maeder, M.S., P.E.
Senior Technical Engineer
chris.maeder@bossintl.com