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

[Andrew Harvey]

On Wed, 23 Dec 2020 at 00:50, Brian M. Sperlongano <zelonewolf at gmail.com>
wrote:

> Great discussion, here and in the 2017 thread.  Participation in the
> tagging list is certainly educational.
>
> water=stream_pool suffers from a few problems, and its use seems far from
> a settled question.  (None of this is meant as criticism, as I understand
> all too well the hard work involved in developing proposals and good wiki
> documentation).
>
> In the three years since that discussion, water=stream_pool has achieved
> just 425 usages.  I assume that the biggest reason for this is that it's
> only documented as an entry in the table for the wiki page for Key=water.
> Notably absent is any mention of stream pools (or for that matter, plunge
> pools) from either of the two main wiki pages for river documentation
> (water=river vs waterway=riverbank).  This begs the question of how
> water=stream_pool should interlace with river polygons for mapping.
>

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.


> Stream/plunge pools are part of a river or stream (I assert this based on
> Wikipedia's definition).  Logically, one might think "chop up the river
> polygon, and tag the stream pool portion as a stream pool".  This approach
> has a few problems:
>
> 1. If the river area is tagged with the water=river scheme, the area of
> the stream pool is no longer tagged as a river (because water=stream_pool
> conflicts with water=river).  This is wrong because the stream/plunge pool
> is indeed part of the river.  You could use the waterway=riverbank scheme,
> but now you're blending the two types of river tagging.  Yuck.
> 2. If the stream pool has a name, that portion of the river loses the name
> of the river, as the polygon can only have one name= tag.  The
> waterway=river way of course would still carry the name, so you do still
> maintain continuity.  But you lose concepts like "the total surface area of
> the river".
>
> Alternately, you could overlap the pool area over the river polygon, but
> then you're double-tagging the water area which seems like poor practice,
> and certainly JOSM would give you a warning for overlapping water features.
>
> It seems to me that river=stream_pool would have been the more sensible
> tagging within the natural=water+water=river scheme, as it further
> describes that portion of the river.
>

So for creeks would you also use river=stream_pool or have also
stream=stream_pool? I guess that's fine too. I see your point, it's just
I'd never really considered mapping streams/rivers with stream pools as
anything other than a linear way.


> The low usage and structural problems associated with stream pool tagging
> suggest that this is not a ready-for-prime-time tagging scheme, and
> deserves a proposal - not just a mailing list discussion - to sort out
> fundamentally unanswered questions about how to tag a river with both named
> and unnamed stream pools, particularly with regard to how the polygons are
> divided and/or overlapped.
>

I don't think changing the tagging would really change the usage, but if
you think there are structural issues with the tag then I'd be happy to try
and comment on a proposal.


> One might also argue that a stream pool should simply be mapped as a node,
> and if it's too big for a node, then perhaps it's more properly tagged as a
> pond or lake.  Unanswered questions.
>

Sorry I disagree with that, because water=pond per the wiki is usually man
made, and they are too small to be a lake and probably formed differently.


> Stream and plunge pools are a part of rivers (per WP definition), and I
> don't intend to address river tagging as part of the reservoir/lake/pond
> proposal[1].  Therefore, what makes the most sense is to simply scrub
> mention of pools and rivers from the proposal and leave it squarely focused
> on reservoirs, lakes, and ponds.
>

Yeah that sounds good, a separate proposal could cover that.

>
> [1] https://wiki.openstreetmap.org/wiki/Proposed_features/Reservoir
>
>
>
> On Tue, Dec 22, 2020 at 12:49 AM Andrew Harvey <andrew.harvey4 at gmail.com>
> wrote:
>
>> Back in 2017 this was discussed on the list
>> https://lists.openstreetmap.org/pipermail/tagging/2017-March/031595.html and
>> the outcome of that was I added water=stream_pool to the wiki at
>> https://wiki.openstreetmap.org/wiki/Key:water#Natural_features. Is there
>> any reason to change this now? I think continuing to tag these as
>> natural=water + water=stream_pool is best as currently documented and in
>> use.
>>
>> On Tue, 22 Dec 2020 at 05:13, Brian M. Sperlongano <zelonewolf at gmail.com>
>> wrote:
>>
>>> Discussion on the current reservoir proposal[1] (which seeks to define
>>> the distinction between reservoirs, lakes, and ponds) has brought up the
>>> question of stream/plunge pools[2,3], and how they fit into the lake/pond
>>> definitions.
>>>
>>> I've come up with the following text:
>>>
>>> "Occasionally a river or stream will form a stream pool or plunge pool,
>>> which are bodies of water that naturally occur along the course of the
>>> waterway. These waterbodies may either be tagged as a lake or (usually)
>>> pond if they are named or significant in size, or else they can be simply
>>> conflated with the river."
>>>
>>> Is this distinction satisfactory?  How are folks tagging these features?
>>>
>>>
>>> [1] https://wiki.openstreetmap.org/wiki/Proposed_features/Reservoir
>>> [2] https://en.wikipedia.org/wiki/Stream_pool
>>> [3] https://en.wikipedia.org/wiki/Plunge_pool
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>>> Tagging mailing list
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>>>
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