[Tagging] Waterway equivalent of noexit=yes?

Paul Allen pla16021 at gmail.com
Fri Aug 14 14:36:32 UTC 2020


On Fri, 14 Aug 2020 at 14:21, Kevin Kenny <kevin.b.kenny at gmail.com> wrote:

>
> The WIki picture of a sinkhole happens to be large, but in karst terrain
> they come in all sizes. https://www.openstreetmap.org/node/5599524737 is
> a sinkhole of quite a small stream.
>

It's been a long time since I've been near (never on) karst.  The stuff I
saw had
no sign of running water or channels at the time but was pocked with many
holes
(presumably caused by rainfall alone) large enough for a person or a sheep
to fall into.

The way the wiki has it, I don't think sinkhole is appropriate for small
streams
vanishing into small holes that even a cat couldn't drop into.


>
> What Mark is showing is usually called an alluvial fan.
> https://en.wikipedia.org/wiki/Alluvial_fan
> Some fans have well-defined (perennial or intermittent) distributary
> streams flowing through them. Often, though, most of the stream channels
> are ephemeral in nature. Sometimes an individual channel was cut in a
> matter of hours by a debris flow coming from upriver.
>

Ah-ha.  I recently saw a network that could be one of those.  Search the map
for "Teifi Pools" then zoom out, a lot.  I fixed some lake names, fixed
which of
two tributaries was the main one on a river and a couple of streams, and
named
a couple of streams.  Oh, and added a dam to a reservoir. I didn't do
anything about
tweaking the waterways that had been crudely mapped, or adding the
tangle of waterways shown on OS OpenData StreetView that haven't been
mapped.  That might be an alluvial fan with intermittent and ephemeral
waterways,
although the slope countours don't seem to support that idea.  Doing a full
tidy-up
on that was more work than I felt like doing, so I didn't worry about it.

I wouldn't even have done that much, but the local newspaper mentioned the
area
and I corrected a few egregious errors as well as adding a locality so that
it
would at least turn up on a search.  Now I've had another look around the
wider area to try to identify if it's an alluvial fan I see more misnamed
streams
and missing streams.  I've just fixed some of them.  I want to forget the
entire place exists - far too much work to do it all right.

-- 
Paul
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