Water levels: What does "mBf" mean? I have seen the term MBf used in a couple of places (a ramp specification and a Hydrological Study) to describe height or depth of water. What is this unit? Can it be converted to meters?

For bonus points: how tall is the ramp at Baja?
It is "mean sea level above the Baltic Sea", in meters (source on page 109). 

That explains why it is used mainly in East-European countries.

Martin Ekman - The Changing Level of the Baltic Sea during 300 Years - A clue to understanding the Earth shortly mentions some historical 'zero points' (page 111). 

As mentioned in the comments: 
mBf means méter Balti felett (Hungarian for meters above Baltic Sea). They also use meters above the Adriatic as a datum (https://en.wikipedia.org/wiki/Metres_above_the_Adriatic, mAf from méter Adria felett).