WIP - The World of Valys (first map attempt)

[Viking]

Hi Lordfly,
Water always flows downhill and takes the path of least resistance naturally so rivers rarely ever split as they go downstream. They tend to do the opposite as different streams and rivers tend to join up into larger single rivers as they get closer to the ocean. As such it is much more likely that a river would have three branches feeding it from different mountain valleys than a river coming from a single source in a mountain would split into three rivers as it flows into the ocean. Deltas will do this like the Egyptian Nile for example but even it only splits into two main branches. Again looking at the Nile however it has numerous more feeding rivers upstream.

Edit:
Look into water sheds and drainage basins as well here