Tag:historic=highwater_mark

A high water mark is a marker indicating a past flood/high water of exceptional height – usually with a date (or just a year). Typically, this is a plaque on a wall, but it can also be something else such as an engraving in a wall, a painted marking on a wall, a pole or a stone with a marking (or several markings).

Tags used in combination

• flood_date=* – the date of the flood written as yyyy-mm-dd
• flood_mark=plaque - a plaque
• flood_mark=painting - a painted mark
• flood_mark=engraving - usually inscription (made on rock, wall)
• flood_mark=pole - usually with several marks
• high_water:height=* – height from the ground
• location=* – indoor, outdoor
• support=* – wall (e.g. a painting or engraving on a wall), wall_mounted (e.g. a plaque on a wall), pole, stone, ...
• inscription=* – the text of an inscription that may be found on the high water mark
• tourism=attraction

Alternative tags

historic=memorial+ memorial:type=flood_mark	Most frequently used (probably by a mapping project in 2016), but the subkey should be memorial=* ...
historic=memorial+ memorial=flood_mark	... however this variant is almost not used.
historic=flood_mark
high_water_mark=yes	It is not clear what object to use this tag with, and this is not a stand-alone top-level tag.

See also this OSM tag history as a curve chart which shows the development of the usage numbers of the different tags in comparison (precise historical data only between 2016–2018).

See also

• High water mark on Wikipedia
• Category “Flood level signs” on Wikimedia Commons
• flood_prone=* – marks a road that is often underwater