Attached Link: This is what I have so far using it. It still needs alot of work tho.

I was just trying this my self and have a decent looking waterfall all done in vue. make a new terrain and go into the terrain editor. limit the height to the height of the waterfall. First do the rocks behind and next to it. Use the raise brush and make the ouline of the waterfall make sure that the are behind the falls is at the same height. Add some fluvial erosions (will add others later). copy this terrain and paste it directly on top of it. this will be the water.  Lower the terrain at the ends of the water so that the rock underneath will show. Add more fluvial errosion. Make sure the water is slightly further out from the rocks. You can go back to the rocks and add grit and stone errosion.to make a river leading up to the falls you can either just raise the water terrain a little and add terrain to either side to close it in more or form one yourself. To form it yourself,  use the dig tool to form the river bed. Copy and paste it as before (dont need to move it at all). Invert the new terain. This is the water. You may have to lower it or flatten it a bit to make it look right.  I hope this helped.