[Tagging] Spillways

[Dave Swarthout]

Weir does not seem appropriate for this type of thing. There is a tag,
waterway=spillway, that seems like a good fit - 81 uses so far.

You could also add emergency=yes to the above or create a new tag,
emergency=spillway

Cheers

Dave

On Wed, Mar 22, 2017 at 12:25 PM, Mark Wagner <mark+osm at carnildo.com> wrote:

> On Wed, 22 Mar 2017 10:44:17 +0900
> John Willis <johnw at mac.com> wrote:
>
> > How do you tag an emergency spillway?
> >
> > I am tagging a giant flood control reservoir in my region. The “lake”
> > is surrounded by giant man-made embankments on all sides, surrounded
> > by an additional  set of embankments, with gates to let the water
> > out. There is no dam per se, because there is ~200 km of this
> > man-made 10-20m tall earthen embankment (levee) around the entire
> > river system - it is part of that.
> >
> > When this levee system fails uncontrollably (like it did downstream
> > from me in 2015), it is really bad.
> > https://www.youtube.com/watch?v=Hfs3OeqiqRk
> > <https://www.youtube.com/watch?v=Hfs3OeqiqRk>
> >
> > This reservoir system catches water during a typhoon from a smaller
> > river, then releases it slowly after the peak flooding into the
> > larger river. this reduces the chance of flooding further
> > downstream.
> >
> > However, it has 2 sets of emergency spillways (each about 1Km long)
> > to let water out of both sets of embankments, so where it “fails" can
> > be controlled. it is 5 m lower than rest of the embankments
> > surrounding the reservoirs. These were recently added.
> >
> > I made a polygon on one such spillway.
> > https://www.openstreetmap.org/way/481898093#map=14/36.2115/139.6880
> > <https://www.openstreetmap.org/way/481898093#map=14/36.2115/139.6880> .
> > the heart-shaped lake is the reservoir, and most of the surrounding
> > green areas are part of the flood control basin made by the second
> > set of levees.
> >
> > These *emergency* spillways are considered safety features of most
> > large water control projects - if the human-controlled gates o the
> > normal spillway jam shut, the emergency spillways will keep the
> > dam/embankments from being over-topped in unexpected places. I know
> > these are a major mappable feature of large dams, but they are not
> > mentioned on the Dam wiki page. Maybe I am looking at it wrong.
> >
> > As these are not a weir, nor a normal path for water to go, I
> > wouldn’t tag them as a weir nor as a object normally associated with
> > a waterway line running through it.
> >
> > is there an existing tag or another name for these features that I
> > don’t know of? How do I tag these emergency spillways (and heck -
> > these huge levee embankments!) correctly?
>
> For what it's worth, Oroville Dam
> (https://www.openstreetmap.org/#map=17/39.54412/-121.49263) currently
> has its emergency spillway tagged as a weir.
>
> --
> Mark
>
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-- 
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com
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