Generally speaking, the steeper the hill the height of the hump increases. The Defender shown (stock standard suspension) has good clearance and for maintained fire trails and forest roads has rarely scraped over these drainage humps (also called spoon drains).

This image is looking down a slope which has been eroded by water flowing unchecked straight down the track forming the rather large rut. In this case the climb could be done fairly easily by staying with both wheels to the left of the rut (in the picture), or by a wheel either side of the rut. ( As this rut continued for some distance, I walked up first and decided where I needed to cross over the rut).

This image is of a much more extreme hump.

A Land Cruiser with a 6 inch lift got up okay, the Defender got up but scraped the top of the hump and the normal Nissan became stuck. It was lowered down the slope to a safe turning location.

4WD Trips does not generally conduct trips with these sorts of obstacles.