Treehugger posted a great link to the something about maps blog, whose author has developed maps of river systems in the style of urban transit maps. The specific inspiration is the famous London Underground map developed by Harry Beck (the first edition of that map is below).
This map has been very influential in how other public transit systems are mapped. Chicago’s CTA train system is a direct descendant:
Daniel P. Huffman, the author of “something about maps,” has made maps for several river systems. Below is his map of the Mississippi River, and its tributaries:
I really like how these look. The information is much easier to grasp in this form than in a more precise representation. The most basic information: where the water begins, its general direction, and where the water ends are all communicated.
One of the best ways I’ve seen this illustrated is with the geographical representation of the London Underground. Compared to the Underground map featured above, the current subway system actually looks more like this:
This is much harder to interpret at a glance (which, let’s be honest, is what most subway travelers do) than the design aesthetic utilized in the Underground map. Applying that sort of thinking to a river map is just brilliant.