[going hot]

Also, most river beds start with a trickle, then join others to form larger and larger channels.

Thus there is feathering at the smaller branches upstream on dry beds.

These beds, and their tribs have rounded ends, more like a flow going in the opposite direction, then cooling off, similar to ice or lava flows on this planet.

At least with the depiction above.

[Openurmind]

In the image I posted above, the elevation does go downhill from left to right. Not right to left. I checked it while I was there capturing it just to make sure.