Click Drawing Tools | Edit Features | Edit Concentrated Flow Channels. Now click the concentrated flow channel you want to edit. The concentrated flow channel you select should now have a yellow outline. To edit the boundary of the concentrated flow channel simply click on the boundary and drag the point to the desired location. If you want to change the type of concentrated flow channel, select it from the dropdown. If its a CAFO you can also change the conduit to navigable water. By checking or unchecking this option a SWQMA will be created or removed. When you are done editing click, Save exclusion area.
Please refer to the video tutorial on Adding Concentrated Flow Channel in SnapMaps for more information.