[Tagging] Definition of lake/pond as applied to stream/plunge pools

[Brian M. Sperlongano]

On Wed, Dec 23, 2020 at 7:17 AM Paul Allen <pla16021 at gmail.com> wrote:

> On Wed, 23 Dec 2020 at 06:21, Andrew Harvey <andrew.harvey4 at gmail.com>
> wrote:
>
>>
>> All the ones I've encountered the stream/river was only ever mapped as a
>> linear way, so it's just a linear way for the stream and then an area way
>> for the stream pool.
>>
>
> That works fine for streams.  It even works for narrow rivers.  It doesn't
> work so well for wide rivers where you map the banks with water=river.
> You can do it that way, but it seems a bit of a kluge.
>
>>
>> So for creeks would you also use river=stream_pool or have also
>> stream=stream_pool?
>>
>
> The only creek I encountered was on a wide river, so I just expanded the
> water=river into the creek.  Maybe we need a water=creek.  Except
> "creek" means different things in different parts of the world, so we'd
> spend forever arguing about the name. :)
>

It seems like the convention for rivers is that the river's continuity (and
name) are carried with the waterway=river ways and not the area polygons
that cover the width of the river (regardless of whether you use the
water=river or waterway=riverbank scheme).  I also note that the
distinction (effectively) between stream/river (the only variants that are
in serious use) is that a stream is small enough that it's modeled by a
way, while a river is large enough to require drawing a polygon.

I will make an assumption that there exists a class of these pools that are
large enough that we would want to be able to map them as an area (and we
wouldn't call them a pond), and there are also some that are small enough
that mapping them as a node or linear way is fine also.

In order to work desirably under a single tag in all cases large and small,
tagging for stream/plunge pools needs to:
1. Work as a node, way, or area
2. Not break the continuity of the sequence of named waterway=river ways
that compose the river
3. Be taggable with name=*
4. Not require way/area duplication
5. Be the same tagging for both rivers and streams

Using water=stream_pool breaks rule #2 or #4 when modeled as a linear way
along the waterway=river.
Something like river/stream =stream_pool breaks rule #5 if both variants
exist.

I think it's fine if a river does not have continuity of water=river or
waterway=riverbank polygons, as long as the waterway=river is properly
contiguous.  I.e. I think it would be fine to have a sequence of river
polygons with a stream pool polygon in between.
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