Very very nice
Most has been said already actually.
Regarding the soil I'd like to suggest to use 3 or 4 fake stone layers at different sizes and different colours.
Don't displace them, just hook a coloured PF to them and give each fake stone layer a (slightly, not too much) different hue for their high/low colours.
For sizes use something like 0.01 meters and smaller.
Especially if you render at detail 1 then you can use tiny stones
Make sure to do crop render tests at final render settings eventually.
I have 1 little compositional remark if I may:
The wild tree (which I like btw!) is too much in the centre.
Since it is casting a shadow to the right I'd like to suggest to move it to the left in the composition in such a way that its shadow is cast on the creek.
This way there's more focus on the creek and the creek itself isn't uniformly lit anymore, which should make it look more interesting.
In the end you may also consider clearing up the very foreground of the creek by slightly moving around those branches.
I'm very curious to see more!
Cheers,
Martin
