Very cool indeed, but I do have a minor comment:
Due to the way you've shown how the Oss flows into the Big Silver River on the city map, I get the impression they flow left to right. But looking at the regional map it's obvious they flow right to left.
Ha Ha! Good eye! The city map of Gerse was created first from notes and a rough outline by the author. All was approved and the final went to press. Later on when I received the art order for the regional map from the editor, I noticed the discrepancy but couldn't go back and change the city map. If the text had allowed it, I would have simply changed the geography in the regional map. But alas, it was already established. The principal river (Big Silver) had to flow east to west and the only way it would have worked was with a super weird oxbow that wouldn't have fit within the landscape. I wish they had assigned the regional map first since then I could have checked the details of the city in context.
A bit of a drawback in creating landscapes from whole cloth is the lack of GIS data or sat photos to check your work against. ;-)