The level is not the depth, though it is related.
The level is relative to some fixed point,
not necessarily the river bottom (which moves).
A new ultrasound-based River Level sensor has been deployed,
affixed under my new footbridge (old bridge washed away in flood).
This measures level of river on my side of island.
The old pressure-based River Level sensor
(transmitter nearly washed away with old bridge)
has been re-positioned 30 meters downriver from island.
This measures level of whole (merged branches) of river.
Old "river level" measures are nearly the same as the