Open Channel Hydraulics - on bend

[KeyboardKev]

I'm using Chow's "Open Channel Hydraulics" to calculate superelevation depths on a channel in a bend. The results give us Delta H. However, no picture is drawn showing what delta H is referenced to: is it on TOP of normal depth, or is it the height differential between the high and low extremes? Thanks in advance!

 

[cvg]

delta h is the change in water surface elevation across the channel