Is the stream running through a basin at the bottom of the hill? It does look like it should slide down southward. The light is coming from the northwest, so the shadows north of the river indicate that there is a slope down to the stream there. But south of the stream, the terrain is still in shadow, which makes it look as though that area is still lower than the stream. What I think you intend, though, is that darker areas are simply lower, in which case the stream is right where it belongs.

You might touch your rooftops with a little bit of grunge. Right now, they look a little "cartoony" against the more photoreal textured ground. Just a little bit of dirtying up should make them look like houses in this scene instead of objects painted on top.