On the geologically plausible front, there are some river layout issues that you may wish to deal with. The attached image has some scribbled notations.

Click image for larger version. 

Name:	Drawn_Map%20(1).jpg 
Views:	193 
Size:	48.9 KB 
ID:	30972

Things circled in red are rivers that are most likely branching the wrong way (rivers tend to join when they go downhill, not branch). The area circled in green is a join between two rivers that is unlikely to occur naturally and is geologically unstable. The areas circled in yellow are most likely too large a distributary network compared to the river size.

I recommend a scale bar for the map to help people get themselves oriented.

If the purpose of the map is to show things in a diagrammatic fashion then the elements described above may be perfectly appropriate.