[Tagging] Waterway equivalent of noexit=yes?

Paul Allen pla16021 at gmail.com
Wed Aug 12 18:27:59 UTC 2020


On Wed, 12 Aug 2020 at 18:06, Joseph Eisenberg <joseph.eisenberg at gmail.com>
wrote:

> Would waterway=spreads only be used for intermittent streams/rivers where
> the waterway spreads out and evaporates on the surface?
>

I hadn't even considered its use with intermittent streams.

>
> If the water appears to sink into sand, gravel or fractured karst rock,
> would we want a different tag instead, e.g. waterway=sink?
>

Not really.  There's no hole it goes down.  At least that's how it appears
on OS
maps.  They show waterways that just terminate, which I assume are sinks
(and we probably need a tag such as waterway=sink for the ones that
aren't big/deep enough to qualify as natural=sinkhole).  Ordnance Survey
also shows, and labels, spreads.

OS appears to have renamed or deleted their terminology pages because I can
no longer find them in Google.  But I eventually found this copy:
https://www.lib.cam.ac.uk/files/os-mastermap-real-world-object-catalogue.pdf
which says:

The source of a river is defined by one of the following terms:
Collects - where the source is a bog or a marsh
Spring - where the source is a natural spring
Issues - where the source is an emission from an agricultural drain, or
where the stream re-emerges from underground

Where a river disappears underground the point will be described Sinks.
Where a river spreads on a sand or shingle beach, or in a marsh, it will be
described Spreads

We have springs and sinkholes.  We don't really need collects if we map the
marsh
and the waterway that issues from it.  For completeness it would be nice to
have
issues, sinks and spreads.  We don't have to copy what others do, but it's
possible they did things that way for good reason...

I understand that natural=cave_entrance can also be used when a waterway
> drops into a sinkhole or other open cave entrance, often found in limestone
> (karst) geology areas.
>

And then forms, at least in part, an underground river.  That's a whole
nother
can of worms.  And doesn't seem to match the definition of spreads.

-- 
Paul
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