Post 5.  Look southwest (downstream).  There is another channel here, although it is very subtle and may be difficult to recognize.  Where did it come from?  Look northeast (upstream) -- there is no source for this channel, nothing to flow into it!  There is only an "escarpment" -- a steeply sloping hill.  The downstream landform is called a beheaded channel.

A stream once flowed downstream into this channel, but motion across the fault has separated it from its original source.  Where is that source now?  The original upstream portion of this channel must lie somewhere to the southeast -- this is because the upstream portion has been carried in that direction by plate motion.