I suspect there may be a big difference in survivability in falls depending upon whether you are talking about urban situations or wilderness environments; aid generally arrives a lot more quickly in an urban setting.

The rule of thumb I developed ater experiencing the results of several fall victims was that fall heights of over 40 feet were usually fatal. I can recall one fatality who fell a mere ten feet and I think I remember one who survived a 50 foot fall. And then there was the guy who fell about 300 feet - definitely DOA.

Much depends upon the surface upon which you land. A rocky surface is typically rather bad. Consider also the nature of the fall. Are we talking a free fall or a sliding fall where the victim might not build up so much speed.

There are instances of climbers surviving fairly long fall - well over fifty feet. Those were cases where the belay system worked to slow down the impact. There are plenty of fatalities at lesser heights as well.

I would not wish to experience a fall of thirty feet, especially a free fall. I have walked away from sliding falls around thirty feet in length - I can recall about two instances, but I an not anxious to push my luck.