“I read somewhere that most direct falls from 30 ft. or more onto a hard surface are fatal”
Essentially true.
There is a very detailed paper from NASA (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930020462.pdf), from which figure 5 (p. 36) is most useful.
The summary is:
It does depends on where and which way up you land - feet-first onto a soft surface is best (pretty obvious).
For a hard surface, assuming you don’t land on your head, up to about 12m/s impact velocity, you are almost certain to survive (corresponding to a fall from a height of about 23 feet). Though “survive” is likely to involve life-changing injuries at the top of this range.
Between 12 and 17m/s, you may or may not survive (corresponding to a fall from between 23 and 39 feet).
Over 17m/s, you are almost certain not to survive (corresponding to a fall from over 39 feet).
Anecdotally, pole workmen and tree arborists seem to cite 9 meters (~30 ft) as the “cutoff” for fatality in a fall — that is, most who fall from thirty feet or higher die.
Mostly agreed (my Dad was a Forester). However, many falls involve landing awkwardly, resulting in one’s head slamming into the surface struck, among other things. Does the NASA study take that into account? And what about fatalities due to long term effects? (I glanced at the paper, but am too tired to read 58 pages...)
Regardless, without immediate treatment, I think most anyone who falls off a “Trump” wall is going to be in a really bad way.