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.

[sgrig]

I don't know whether you could do that, but the easiest way is to replace rivers with sea tiles.