I'm not following your description.
Is the concrete to add support and height and the rock will be on top/in front?
To add height to pur upper ond section, we used lanscape bricks, the kind that lock together when you stack them. You can't see them from the front viewing area as we covered them with rock. But if i ever change my mind design-wise (which i do almost every year to DH's dismay!) we can move them easily. Also if there is a plumbing issue under there, it can be rectified.
We are zone 5, Michigan, lots of freeze/thaw cycles and horrible winters.
In the picture, the upper pond waterfall section is about 3 feet higher than the lower, you can see the rock in front of the brick. We are thinking of building an additional waterfall behind that upper section next year, using the same technique.