Rivers in karst areas may flow underground in some sections. Exampe: Note: 5263116 | OpenStreetMap
How do I tag this river correctly?
Currently it’s tagged underground=yesand layer=-4 but is rendered like any other surface river.
At least here OpenStreetMap they tagged it as tunnel.
There are 4 known underground connections between Danube and (Radolfzeller Aach, Lake Constance) Rhein river
In my opinion, underground rivers should only be mapped if their course is reasonably well known. Just because a river disappears underground at one point and reappears at another does not justify drawing a straight connecting line.
A relation would actually make more sense, similar to what is proposed here for underground power lines:
When I look at your example @ToniE, it hurts my eyes.
5 Likes
Yeah, mine also.
I don’t think I would use tunnel unless the underground path of the waterway was man made.
Also, note that the Mojave River flows underground for most of its length even though it is not in karst terrain and that its course is well documented. So, there are other possibilities for underground rivers rather than flowing through cave systems.
4 Likes
Hog Canyon Creek flows through a talus slope for about a hundred meters from the foot of the falls to the shore of Hog Lake. It’s currently mapped as a tunnel, but it isn’t one by any reasonable meaning of the word.
1 Like
In the case that triggered my question, the course of the river seems to be very well known (it’s not me who mapped that river; I know nothing about it): Way: Pivka (710342972) | OpenStreetMap
The way appears heavily overtagged to me.
Hello
We had this discussion before (several times maybe). From my memories, it’s related to Proposal:Hydropower water supplies - OpenStreetMap Wiki
This attempt may help: File:Waterway flows.png - OpenStreetMap Wiki
We considered natural=cave, but there are many other ways of flowing water underground instead of a cave.
I agree on using tunnel=* on man made structures only and preserve waterway=* for actual water flows and not for containing structures (whatever natural or man made)
My 2cts!
1 Like
OK, I’ll tag it accordingly.
Looks like there is an opportunity to draft a proposal if anyone is motivated…
as for unknown geometries that are rendered as a a straight line, it is arguably a rendering issue (given that the appropriate tags are defined): a way with just two points can be interpreted as ingress+unknown+egress, and rendered appropriately (e.g an arbitrary curve, or a fuzzy surface)
Better tagging would be location=underground in that case (there are already 69k waterways tagged with location=underground).
layer is only meaningful when dealing with a related set of ways which need to be ordered, e.g. roads/bridges/tunnels. It is not how to indicate that a feature is underground.
5 Likes
tunnel=culvert is commonly used in the UK, eg. Way: River Neckinger (1501792130) | OpenStreetMap
A culvert is something built by people, the other examples of underground rivers were not
4 Likes
Some in the underwater caving world use syphon to describe the cave carrying water between sinkholes (cenotes).
The interlinking of sinkholes can be very complex, mapping them tends to be limited by the cave size a diver can squeeze through. No doubt there are many smaller linked routes in such karst systems. Not really rivers, but there are some rivers that flow through the systems too.
Other parts of the world have partially flooded systems so you can walk or crawl between the flooded parts,sumps i think they’re called.