waterway=stream + tunnel=flooded isn't rendered as a tunnel

[Nekzuris]

waterway=stream + tunnel=culvert ✔️ waterway=canal+ tunnel=flooded ✔️ waterway=stream + tunnel=flooded ❌ is rendered as a normal stream, should be tunnel

[imagico]

Thanks for the suggestion.

waterway=stream + tunnel=flooded is used <1000 times with many use cases clearly synonyms for the more common tunnel=culvert.

We render waterway=canal + tunnel=flooded with a tunnel signature since #4087, it is now predominantly and very consistently used for Qanats, which calls for addressing #3354.

Closing this as wontfix/duplicate of #3179 - since we made the decision in #4087 to selectively only support tunnel=flooded on waterway=canal. Should tagging practice change this can be re-assessed.

As said before a more comprehensive look at the whole artificial water infrastructure domain and how to render this in a consistent and differentiated fashion would be very desirable - see in particular #3180, #3354, #4405 and https://github.com/gravitystorm/openstreetmap-carto/pull/4087#pullrequestreview-382783504

[Nekzuris]

I don't understand how you can defend the idea that something tagged as tunnel=* should be rendered like an open river, even if the tag has low usage.

There are very legitimate cases of waterway=stream + tunnel=flooded, but obviously, if you render them as visibly as an open river, mappers will change them to tunnel=culvert because it spoils the map.
waterway=canal + tunnel=flooded would be a closer synonym, but since you don't take its width into consideration and small canals are rendered as big ship canals, it doesn't work either.

[imagico]

I don't understand how you can defend the idea that something tagged as tunnel=* should be rendered like an open river, even if the tag has low usage.

We render tags, not keys. And i have explained that currently tunnel=flooded is - in combination with waterway=stream - predominantly used as a synonym for tunnel=culvert. I am not sure what is not understandable about that.

As said there are <1000 uses of that tag combination, there is no documentation on what this combination is supposed to mean, You have provided no example of how the tag is used in a distinctly meaningful way or a description of how you think the tag should be used that we are supposed to support with our rendering. That IMO leaves zero basis to even consider supporting it at this time.

Regarding rendering of waterway=canal - we already have #3354 for that. Contributions there are welcome, previous discussion there points into various directions where this might go.

[Nekzuris]

This is a small flooded tunnel coming from a small dam that diverts part of a small stream into an artificial lake.

[imagico]

I don't think it is anywhere close to global consensus to map penstocks as waterway=stream. If it is in your local community then you should document that somewhere. Right now neither the English nor the French wiki page on waterway=stream suggest anything in that direction.

[Nekzuris]

You're right, it should be a canal because it's artificial, but since it's only a fraction of a stream less than a meter in width, the current rendering isn't appropriate. I think the tunnel is 0.3m in width.