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).
Anabranch sensor:
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.
Merged sensor:
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
Anabranch level.
