Rik - Nice map.
The things that I reallly liked were:
- The color shift for the higher elevations.
- The seeming (whether intended or not) effect that the elevation had on the streets in the city.
- The fact that you thought about and included a flood plain on the map.
Might I suggest that you shade the water according to its depth, i.e. darker blues for deeper and deeper water.
I'll continue to think on it, but it's a really good start.