Add river to my capital county of thomond?

[ModsNewbie]

As you probably know, my capital county of thomond is basically a natural fortress with river that protects all sides except the one facing hy_many.

I wanted to change it to make it even more perfect but I am at a loss to how to do it.

I looked up both terrain.txt and thomond.txt in province history folder but they do not seem to carry the info. I need to change.

Please help!

 

[Arko]

You need to alter rivers.bmp file