Yeah that would be considered isometric. Don't worry about the terms though because it's not like we use the term accurately, it's more of a style description than it is it's technical meaning. On this board in terms of regional maps it basically means a pictorial representation of symbols that includes a part of their profile or side view, generally from a high angle.

Waterfalls are difficult, but I'd say what you got there is a good enough base if you wanted to refine it further. I would note that water falls are almost always white because the water breaks apart as it's falling and gets heavily aerated. Same thing with the plume it sends up as the it crashes into the bottom.