> On Jan 11, 2019, at 3:00 PM, Marc Gemis <marc.ge...@gmail.com> wrote:
>
> was always under the impression that the ones I encounter between
> farmland and meadows, which typically are surrounded by dirt, ground,
> plants are ditches. That drains are constructed with concrete or
> similar material and that there are normally no plants on the bedding
> of the drain.
TL;DR - the connotation of “drain” is a problem. it is not “draining away”
unwanted water, it is merely moving it around, and this connotation causes
mapping issues.
~~~~
I like this summary too. I think the issue is that “drain” has a connotation of
moving water “away” from some spot where it is no longer needed or has been
used - which is confusing for a lot of irrigation uses.
In places like southern California, which only have large (5x5m) open-air
aqueduct systems to move usable water, and further distribution handled almost
100% by pipe for irrigation or drinking. sewer is also piped and handled by
treatment plants, and “storm drains" merely channel the occasional rain to the
ocean.
This makes mapping “drains” and "ditches” is super easy, because almost all
drains/ditches are moving unwanted rainwater to a waterway/ocean.
but in my area of Japan, each neighborhood has several *Kilometers* of tiny
concrete roadside “drains” (covered and uncovered) that have little doors or
valves that farmers can open to flood ditches that flood rice fields. there are
side channels, small storage ponds (3x3m), and other very detailed and
intricate water management systems that make a Californian like me marvel at
the rain management system they have created. The drains act merely as storm
drains the rest of the year, and integrate “streams” and other natural channels
sometimes. but the rain they move is useful for irrigation; rain “drained” away
from my area is actually irrigation water for people further downstream.
the other issue is scale. some concrete drains are very tiny measure less than
20cm2, though most are 30cm2 or 50cm2 . most ditches are also roughly 30cm2.
if we go by construction, and try to remove connotation of wastewater, then I
think it is easy to map.
Javbw
_______________________________________________
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging
