Pocus had a look to the backup files and has found the answer :
l'interdiction vient de Forrest et de ses canons... Effectivement pour cours d'eau mineur c'est peut être abusif et en tout cas pas clair du tout pour le joueur. Je pense que je vais le restreindre aux cours d'eau majeurs.
Next to Memphis region (on the east side) was Forrest with a corps and cannons. He was creating an interdiction on the Loosahatchie river (the one between Covington and Memphis).
Pocus agree that such an interdiction could be excessive and at least not clear for the player. He think this "feature" will be retricted to major waterway.
I do not remember that such a behaviour exists in previous version (but perhaps I failed to see it). Does someone know ?
Moreover I hardly understand it : a player could hinder any river crossing just by the presence of some artillery

?
I'm disappointed : this rule makes me fail an attack on Nashville and makes me loose several brigades that were forced to move in ennemy region.
