Date: Wed, 16 Jan 2019 15:38:13 +0300
From: Eugene Podshivalov <yauge...@gmail.com>
To: "Tag discussion, strategy and related tools"
<tagging@openstreetmap.org>
Subject: Re: [Tagging] Drain vs ditch
Can you jump over a drain or ditch? I find the jump over information well
chosen for streams and most important property when actually walking in an
area and trying to find a way through.
In the place where I live drainage ditches are 1-5 meters wide and you can
hardly jump over them. Even if they are 1m wide you would not risk jumping
over them because they are located in wetland and have swampy banks. They
usually have a lot of culverts to cross them over.
Somehow it is not satisfactory to distinguish irrigation from drainage for
lined watercourses on the main level
You are right, irrigation ditches can be lined along their way to a field
but when on a field they may be unlined to let water soak into the land.
Drainage ditches are always unlined because they collect water from land.
Drains are always lined (or should be lined on good terms) because they
carry liquid away without letting it soak into the ground.
If you find the above statements correct (I don't know, may be in other
countries it works differently), then the "lined" characteristic lets you
distingish between drainage ditches and drains easily. The only thing we
need to resolve yet is to let irrigation ditches be linied. Here is how we
can complement the definition of ditch to respect this.
ditch - Small artificial free flow waterways used for irrigating or
draining land as well as for deviding land. Irrigation ditches can be lined
or unlined, drainage ditches are usually unlined. Consider using
waterway=canal for large irrigation or land drainage channels. Consider
using waterway=drain for lined superflous liquid drainage channels.
PS: I'm not a native English speaker, so probably someone could formulate
it in a more beautiful way.
Cheers, Eugene
[...]
I'm glad your definition does not require ditches be unlined. In the US
we have many highway ditches that are unlined, except for the steepest
part, typically where they empty into a stream. These areas are
sometimes lined with concrete to prevent erosion. If I were to map one
of these, I would consider the whole thing a ditch. I would not
consider part of it a "drain," simply because it's lined.
Mark
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