Drain vs ditch

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Re: Drain vs ditch

Graeme Fitzpatrick

On Fri, 22 Feb 2019 at 20:48, Eugene Podshivalov <[hidden email]> wrote:
The primary concern of mine about the current definitios of drain and ditch is that some people are differentiating them by size.

or stay close to dictionary definitions which assumes some overlapping between the meanings. Here is an example:
drain - a narrow artificial open-air channel that takes away waste liquids or rainwater
ditch - a narrow channel dug at the side of a road or field to hold, bring or carry away water

I'd agree that you can't differentiate between drain & ditch based on size (except they're both smaller / narrower than a canal), but you also can't pick them based on locations - either of them can run alongside a road, or go across a field

I'd suggest we just stick with the simple definitions based on lined / unlined that I thought we all sort of agreed on, way back up there ^ :-)

=canal: Use waterway=canal for large man-made open flow (free flow vs pipe flow) waterways used to carry useful water, usually for transportation, but also for hydro-power generation or irrigation purposes

=drainUse waterway=drain for artificial waterways, typically lined with concrete or similar, usually used to carry water for drainage or irrigation purposes.

=ditchUse waterway=ditch for artificial waterways, typically unlined, usually used to remove storm-water or similar from nearby land. They may contain little water or even be dry most of the year – to mark this intermittent=yes may be used.

Thanks

Graeme

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Re: Drain vs ditch

Peter Elderson
This will not suit the situation in Nederland, as explained earlier in this thread. We would have tons of exceptions on all the ‘ usually’s’ and ‘ typically’s’.

Fr gr Peter Elderson

Op 23 feb. 2019 om 00:09 heeft Graeme Fitzpatrick <[hidden email]> het volgende geschreven:


On Fri, 22 Feb 2019 at 20:48, Eugene Podshivalov <[hidden email]> wrote:
The primary concern of mine about the current definitios of drain and ditch is that some people are differentiating them by size.

or stay close to dictionary definitions which assumes some overlapping between the meanings. Here is an example:
drain - a narrow artificial open-air channel that takes away waste liquids or rainwater
ditch - a narrow channel dug at the side of a road or field to hold, bring or carry away water

I'd agree that you can't differentiate between drain & ditch based on size (except they're both smaller / narrower than a canal), but you also can't pick them based on locations - either of them can run alongside a road, or go across a field

I'd suggest we just stick with the simple definitions based on lined / unlined that I thought we all sort of agreed on, way back up there ^ :-)

=canal: Use waterway=canal for large man-made open flow (free flow vs pipe flow) waterways used to carry useful water, usually for transportation, but also for hydro-power generation or irrigation purposes

=drainUse waterway=drain for artificial waterways, typically lined with concrete or similar, usually used to carry water for drainage or irrigation purposes.

=ditchUse waterway=ditch for artificial waterways, typically unlined, usually used to remove storm-water or similar from nearby land. They may contain little water or even be dry most of the year – to mark this intermittent=yes may be used.

Thanks

Graeme
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Re: Drain vs ditch

Hufkratzer
In reply to this post by Graeme Fitzpatrick
On 23.02.2019 00:09, Graeme Fitzpatrick wrote:
 > [...]
 > =drain: Use waterway=drain for artificial waterways, typically lined
with concrete or similar, usually used to carry water for drainage or
irrigation purposes.
 > [...]

Irrigate with drains? This was the original question of the whole ditch
vs. drain discussion (see
(https://lists.openstreetmap.org/pipermail/tagging/2019-January/042047.html).
It seems to be a contradiction to what wikipedia explains (and therefore
is difficult to remember):

https://en.wikipedia.org/wiki/Drainage: "Drainage is the natural or
artificial removal of a surface's water and sub-surface water from an
area with excess of water..."

https://en.wikipedia.org/wiki/Ditch: "A ditch is a small to moderate
depression created to channel water. A ditch can be used for drainage,
to drain water from low-lying areas, alongside roadways or fields, or to
channel water from a more distant source for plant irrigation..."

And we already have irrigation mentioned on the OSM wiki page for ditch
and not on the OSM wiki page for drain. I think these current
definitions should be changed as little as possible.

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Re: Drain vs ditch

Paul Allen
On Sat, 23 Feb 2019 at 17:19, Hufkratzer <[hidden email]> wrote:

Irrigate with drains? This was the original question of the whole ditch
vs. drain discussion (see
(https://lists.openstreetmap.org/pipermail/tagging/2019-January/042047.html).
It seems to be a contradiction to what wikipedia explains (and therefore
is difficult to remember):

As I see it, ditches are unlined.  They're essentially trenches that are intended to have water in
them.  In areas with a lot of rain (like mine) they allow for the drainage of fields where the water
table is close to the surface.  In dry countries they can serve the purpose of irrigation (in which
case they tend to be interwoven with fields rather than at the edges).  We don't have words for
"big ditches" or "very big ditches", they're just ditches.

As I see it, drains are lined.  They're intended to transport water from A to B either for the purposes
of drainage or irrigation.  Which is a little counter-intuitive, until you think of a drain connecting
a reservoir of water higher than a field to one or more ditches around or in that field.  You build
a drain rather than a ditch in that case because you don't want the water seeping away between
the reservoir and the irrigation ditches.  But it's still a drain because it's draining the reservoir
(that's the bit that's counter-intuitive until you think about what is being drained).  If it's a big drain
then it might be better tagged as a canal (that's a different endless discussion we can have in
another thread).

Trying to call big ditches drains is, in my opinion, a bad move.  Ditches are permeable and
drains are not.  Ditches allow the seepage of water to or from the ditch and the land surrounding
it; drains prevent such seepage.  Lined/unlined (alternatively seepage/no seepage) are the key
distinctions.  Maybe we need a way of specifying the width to avoid people tagging a ditch as
a drain, or vice versa, to achieve different rendering.

--
Paul


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Re: Drain vs ditch

Hufkratzer
On 23.02.2019 18:47, Paul Allen wrote:
[...] As I see it, ditches are unlined. [...]

I googled for "ditch lining irrigation" and got these examples for lined ditches:

- http://www.northwestlinings.com/services-available/installation-services/irrigation-ditch-liner-system/
- http://www.skidmarkgeomembrane.com/Ditch-Lining.html - Irrigation Ditch Lining
- http://www.smartditch.com/markets-agg-irrigation.html - "SmartDitch"


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Re: Drain vs ditch

Paul Allen
On Sat, 23 Feb 2019 at 23:33, Hufkratzer <[hidden email]> wrote:
On 23.02.2019 18:47, Paul Allen wrote:
[...] As I see it, ditches are unlined. [...]

I googled for "ditch lining irrigation" and got these examples for lined ditches:

- http://www.northwestlinings.com/services-available/installation-services/irrigation-ditch-liner-system/
- http://www.skidmarkgeomembrane.com/Ditch-Lining.html - Irrigation Ditch Lining
- http://www.smartditch.com/markets-agg-irrigation.html - "SmartDitch"

They all appear to be conversion kits.  For people who did their irrigation on the cheap and
used a ditch to deliver the water to the irrigation ditches instead of using a drain and then
found they were losing too much water.  You can get away with a ditch for delivering irrigation
water, but it will be inefficient.  You can't use a drain at the edge of a field to lower the water
table.

Yes, we can merge the tags and have drain for both.  And then have to create a lined=yes/no
subtag to differentiate.  Or we can use, as some suggest, ditch for narrow and drain for wide,
and then have to create lined=yes/no and width=n (which might be useful anyway).  It seems silly
to move away from UK usage of ditch/drain and introduce ambiguities that we then have to
resolve a different way.  YMMV.

--
Paul


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Re: Drain vs ditch

Eugene Podshivalov
вс, 24 февр. 2019 г. в 02:56, Paul Allen <[hidden email]>:  
Yes, we can merge the tags and have drain for both. 
I'm still wondering why "drain", not "ditch", should be kept in the case of merging the tags.

Cheers,
Eugene

вс, 24 февр. 2019 г. в 02:56, Paul Allen <[hidden email]>:
On Sat, 23 Feb 2019 at 23:33, Hufkratzer <[hidden email]> wrote:
On 23.02.2019 18:47, Paul Allen wrote:
[...] As I see it, ditches are unlined. [...]

I googled for "ditch lining irrigation" and got these examples for lined ditches:

- http://www.northwestlinings.com/services-available/installation-services/irrigation-ditch-liner-system/
- http://www.skidmarkgeomembrane.com/Ditch-Lining.html - Irrigation Ditch Lining
- http://www.smartditch.com/markets-agg-irrigation.html - "SmartDitch"

They all appear to be conversion kits.  For people who did their irrigation on the cheap and
used a ditch to deliver the water to the irrigation ditches instead of using a drain and then
found they were losing too much water.  You can get away with a ditch for delivering irrigation
water, but it will be inefficient.  You can't use a drain at the edge of a field to lower the water
table.

Yes, we can merge the tags and have drain for both.  And then have to create a lined=yes/no
subtag to differentiate.  Or we can use, as some suggest, ditch for narrow and drain for wide,
and then have to create lined=yes/no and width=n (which might be useful anyway).  It seems silly
to move away from UK usage of ditch/drain and introduce ambiguities that we then have to
resolve a different way.  YMMV.

--
Paul

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