As I was walking around I found a couple "waterfalls" created where a river crosses a ridge, It looked pretty weird, like an homogeneous modelling clay layer on top of the ridge.
I think it would look pretty cool if water created a little falling effect on places like this, with white bubbles being formed at the bottom of the fall like in real life.
This is just a graphical suggestion, the way the game is now does not prevent gameplay in any way, I just think it would look cool and more life-like this way.
Also, we could get a sound of rushing water falling down? Waterfalls are pretty noisy.