Big zoom of the image - made in the open CC3 program.

Then I place my city or any other icon, and in this case, I use trees to hide the mouth of the river

Hide the origin of the river with trees and... now the cat's jump... in this case the river... the biggest imperfections are not its contact with the symbols. These are the curves with strong corners of the fractal node... precisely where I try again to "hide" the imperfection with some icon... in this case trees.

Another option is make a mini valley between hills of groups that go faster. Put a river.

Now the next step is obviously to hide the river's imperfections. In my overland experience, the problems always lie at the origin of the river and where it meets the sea. At the origin it's always easy, I always hide it with trees. The next step is to arrange the trees to be compatible with the slope of the terrain. as you can see in the red arrows.