Physics kills and maims. We accelerate 32 ft/sec each second. Distance = 16*(seconds - squared) so SQUARE ROOT OF (Distance/16) = Seconds. 5280 ft = 1 mile and 3600 sec = 1 hour.

Putting it all together, your speed of impact in MPH is 5.54 X square root of height in feet.

So if you are 16 ft up, you hit the ground at 5.455 x square root of 16 = 5.455 x 4 = 22 MPH. The ground does not give much, so that is like a fast run into a wall. At 30 ft up, you multiply 5.455 times the square root of 30 to get almost 30 MPH, which would be like jumping out of a car in city traffic and hitting a wall. And if you hit a rock, log, etc, you are in real trouble.

Even at 9 ft up, you are hitting the ground at 3x5.455 = 16MPH.

This assumes no parachutes!