On Wed, 12 Aug 2020 at 18:06, Joseph Eisenberg <joseph.eisenb...@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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