Accessing this channel will depend upon whether you can land on the island and walk up to the upstream end of the island, and then whether it is possible to safely launch into the flows up there!
Additional bedrock ledges (likely similar to those in the first channel) populate the
channel to the left of the 'decent-sized island'.
Another drone-video shows this area at lower flows:
https://youtu.be/byoZndxKmtk(Again, I've cued the video to skip lift-off and travel upstream to the channels.)