Rivers played very important role in pre and early industrial warfare. They were channels of communication, supply routes and were ussed for transporting troops ( especially siege trains)
Important fortreses like Maastricht, Azov, Tzaritzin or Torun (Thorn), guarded key waterways.
During war of spanish succesin Marloborough was launching some key operation staying close to river valleys to keep his troops suplied ( he did it during his 1705 invasion of France.
Ageod engine managed to represent importance of rivers its games. WIA with rivers and lakes conecting british collonies with canada is perfect example. Playing French and Indian War scenario one can see how riverine transport can save or destroy supply situation of troops or allow rapid deployment of additional forces.
Civil War II with its enormous importance of Missippi river as highway to invade or defend souther state is another example.
On the other hand in AJE or BOR rivers are not that important.
I guess that massive armies of Spanish Succesion wont be transported with river ships yet i guess there should be some way to show how impornat they were for supllying troops.
My question is how will the game aproach river issues?
As WIA example shows even with the simple supply system one can reflect the importance of rivers.
How will it be done in Wars of Succesion?