On Wed, 22 Mar 2017 10:44:17 +0900 John Willis <jo...@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 _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
