I think if you put in some shadows it would help a lot. I would also take the smudge tool and drag your Dock Pylons down into the water which will give them the look of blurring as they go down into the water. I'm not sure what term PS uses for 'smudge' but I'm sure it's close. One other thing you may want to create a little more rapids coming out of the chasm to help with the depth illusion. I think you may need to do something with the way the structures sit on the land. Right now it looks like they are not quite integrated into the piece. With the straight edges along the bases (for instance the bridge) it makes it look like brand new construction or pre-fab dropped in.
Now this may be an area where I differ from many here in that I don't particularly like lines. Probably something my high school art teacher said but there are not really a lot of straight lines in life. It's all light and shadow. You can use lines but you run the risk of looking cartoonish. That may be fine if you want that style obviously. Perhaps a few tufts of grass or something might help?
I did a quick and dirty mock up for the shadows and pylons just to see if I knew what I was talking about and not all the shadows are in there but if you like what you see I hope it helps. I'm not entirely sure what everyone else is looking at so it would be good to also see what jz has to offer.
You have a good thing going here so don't give up. I know it can be frustrating when people are trying to explain stuff you just don't see. Happens to me quite a bit as well but if you can keep swinging your hammer at it and you will be glad you did.
Oh, and feel free to ignore this post if I have failed to communicate adequately. Most of us aren't trained teachers so sometimes what we try to say just fails. At least we are all rooting for ya