I started the sketch with a small oval shape and gradually filled it in beginning with some large rocks on at the bottom and on either side of the paper.

Between the rocks at the front, I put in a large waterfall and above that a few rapids and above that a smaller waterfall.
On the left side I put in a few smaller trees with their branches curving toward the center.
I added a few more rocks and some smaller trees on either side of the water.
I will post this piece at a later date once I have started adding colour.