I read the topic about realistic rivers features a while ago, and I thought about it while drawing the map.

The split river is in fact caused by a terrain feature, called Racine-des-Monts (Mountains' root) which is located just south of the town of Deux-Rivières. It looks the same way that sometimes a tree's root comes over the ground, except it's a huge rock. This is why it's called that way. I guess that, since water always uses the easiest way, it would be logical that river would split there, since the landscape there is mostly soft ground. To the north, the town of Deux-Rivières is located on a plateau largely made of shale that ends in high cliffs at the sea, so there is no way for the two parts of the river to join again before the sea.

I know this kind of feature doesn't really exist in our world, but I thought it might be pretty logical... don't know what you think of it...