Making rivers impassable?

[Feet]

Would this be possible? For the scenario I'm building, making rivers impassable except at certain points (fords and bridges) is a pretty big strategic idea that I want to implement.

So can they be made impassable and can you add in things like bridges or fords where you can cross a river?

Thanks alot.

 

[lawine]

there have been military units throughout history that could traverse even the deepest river in formation, so you might restrict it to certain units. i know for instance the batavian cavalry was famous for it's ability to quickly traverse rivers/water in formation.