There's nothing running the full width of the bottom edge, but there are 4 folded V-shaped vertial wedges/braces supporting the face of the dam against the OEM bumper. Sort of like this:
The curved sides of the dam are reinforced at the bottom edge by a wide lip on the inside that goes from the outermost of the 4 braces, around to the edge of the wheel arch.
I've taken it up to 100 km/h so far, with no visible deformation ... only checked afterwards, though. I didn't rig my web cam for a live view.