Navigable Rivers?

[Tellos Athenaios]

I was under the impression that shipping troops via major rivers was a fairly common practice.

Yes but there's a small difference in having some ferry going up & down and having a *war* fleet sailing up & down. Navigable rivers would be navigable by even the heavies kind of warships we'd include. The Tiber (for instance) definitely does not qualify: in this context it's not a mere triviality that the Romans preferred to unload the large mercantile ships elsewhere and ship the cargo to Roma using lighter vessels.

The question with navigable rivers (if it would be implemented because navigable rivers also mean 'no roads for you' AFAIK) is: what provinces have rivers that are so deep even heavy warships can sail up & downstream safely?