You're kidding right? I wade rivers all the time and anything over mid-calf with any force behind it is difficult. Slow water - drifting along at 1 to 2 mph - can easily be waded to about chest height. Fast water , which is what we get in flash floods around here, is extremely dangerous. Some of them move with enough speed to out run cars, for example the Big Thompson flood of 1976. Another, in the early 1900, washed a train off the tracks outside of Pueblo.