While checking out the Ob and Irtysh Rivers in Russia, I found the pathological planimetry on the Chulym. It certainly represents a transition of some kind...effectively a complete reversal of direction over a considerable distance. Imagine the absurdity of running a shipping lane on a river like this (not that I know there is one...actually hope there isn't).

Follow this RYHNHO (river-you-have-never-heard-of) both up and downstream and you will be amazed.

http://www.flashearth.com/?lat=56.072215&lon=89.599623&z=10.9&r=0&src=msl