Everything you see was required by the game designer. For example, the gate doesn't make sense out of context, but within the narrative of the town's history, they are trying to build a wall around it, to give it added protection, as it grows and more money flows through. He decided that's where they started, as most traffic come from that direction and people often take boats back down, using the river for ease and speed. The main export of the town is silver. To the north, off of the map are the silver mines.

He felt they would start with the gate and towers, because they could provide a place to watch the road and surrounding area. But the building of the wall stalled and so from the second to third map, doesn't change.

On the first map, you can see the there are small wooden squares, platforms, that served as the first watch posts. There's several scattered about. There's a lot bandit activity and trappers and hunters, so they like to know what's coming in advanced.

As for the river forking, in my mind, it comes back together off the map.