[Tagging] Tagging estuaries: estuary=yes or river=estuary?

Joseph Eisenberg joseph.eisenberg at gmail.com
Tue Oct 29 01:43:45 UTC 2019


"An estuary is a partially enclosed body of water, and its surrounding
coastal habitats, where saltwater from the ocean mixes with fresh
water from rivers or streams" -
https://oceanservice.noaa.gov/education/kits/estuaries/estuaries01_whatis.html

Some tidal channels are part of an estuary, but others open directly
onto the ocean and are not connected to a river at all. For example,
this is common in mud flats along the north sea, and in mangroves
along tropical islands, where the mangroves are completely in salt
water, and there is no mixing with fresh water. Some other tidal
channels are part of an estuary system.

While it would be nice to eventually have sub-tags like esturary=* for
the different types, we first need to define how to map the basic
feature.

My proposal is to map the inland, upper limit of the estuary at the
limit of the tidal area, for river estuaries that have a strong tidal
influence, or the limit of mixing of saline and fresh water. This
point should also be where the river level is at the same elevation as
the coastline (the mean high spring tide line). See also
https://wiki.openstreetmap.org/wiki/Proposed_Features/Coastline-River_transit_placement
- so the coastline would be placed there.

There is also a proposal to map the mean low spring tide line, the
lowest tide line along the coast:
https://wiki.openstreetmap.org/wiki/Proposed_features/Tag:natural%3Dmean_low_water_springs
- so the estuary could end at the point where this line meets the
mouth of the river.

This would usually be different than the political "baseline", which
is often further out to sea, though sometimes it would match.

- Joseph Eisenberg

On Tue, Oct 29, 2019 at 8:49 AM Clifford Snow <clifford at snowandsnow.us> wrote:
>
> A friend, who works in this area of research, pointed me to an easy to read article [1] on estuaries. According to the article there are five types of estuaries based on their geology, coastal plain, bar-built, deltas, tectonic and fjords. (Note I'm skipping the classification based on water circulation as I'm not sure it's appropriate for OSM.)
>
> If we are going to tag estuaries then it makes sense to add in the geology classification system.
>
> Based on how NOAA classifies estuaries We should add to waterway=riverbank + riverbank=estuary + estuary=costal_plain|bar-built|delta|tectonic|fjord.
> The alternative would be to use waterway=estuary + estuary_geology=costal_plain|bar-built|delta|tectonic|fjord.
>
> This would conflict with the wiki article on tide channels [2]. From my reading of the definition of an estuary, it seems that the tide channel is actually part of the estuary.
>
> [1] https://oceanservice.noaa.gov/education/kits/estuaries/estuaries01_whatis.html
> [2] https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dtidal_channel
>
> Best,
> Clifford
>
> --
> @osm_washington
> www.snowandsnow.us
> OpenStreetMap: Maps with a human touch
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