[Tagging] Feature Proposal - RFC - Check dam

[Enno Hermann]

 <https://goo.gl/maps/PrtuW627ndkc3NbX7>

On Mon, Jun 7, 2021 at 6:03 PM Mateusz Konieczny via Tagging <
tagging at openstreetmap.org> wrote:

>
> https://wiki.openstreetmap.org/wiki/File:Check_dam_on_Miya_River_(Jinzu_River).jpg
> for me it looks like waterway=weir
>
> "Solid check dams usually have water flowing over only a small part of
> their width and
> are designed to handle sudden increases in water flow."
>
> Are you sure that thing depicted on image is not also a weir?
>

I agree that it's not the best example and from this picture alone it could
be hard to tell, although the construction is typical for check dams. I
managed to find the location and on Google Streetview (
https://goo.gl/maps/PrtuW627ndkc3NbX7) or the Japan GSI seamlessphoto
imagery (https://osm.org/go/7QeF1CmI6) the water level is clearly different
and water seems to be flowing only through the bottom of the structure.
Given that, the mountainous terrain and similar structures nearby I would
say it is clearly a check dam.


> And "designed to handle sudden increases in water flow." is applicable to
> any sanely constructed waterway engineering.
>

"sudden and significant" might fit better. Often those streams are normally
only a trickle or even completely dry but then can see sudden debris flows
like this: https://www.youtube.com/watch?v=2Rfuoylv34k This is different
from floods on already larger rivers.


> See
> https://en.wikipedia.org/wiki/File:Culverts_under_yass_river_walkway_weir.JPG
> on Wikipedia weir page.
>
> Or https://en.wikipedia.org/wiki/File:Grial%C3%ABces_cuecenes.jpg with
> description
> "During periods of high river flow, this nineteenth century weir of
> porphyry stone on
> a creek in the Alps would have significantly more water flowing over it."
>

An early example of a check dam? ;) I'd say very small structures or simple
constructions that can't be clearly identified as a check dam may just be
tagged as weirs.
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