[Tagging] Spillways

John Willis johnw at mac.com
Thu Mar 23 00:08:32 UTC 2017

Ah yea, emergency=yes is bad.

3 questions: 

- mapping levees/dykes with additional area extent tags (like river+ riverbank) 

- mapping spillways in a similar fashion. 

- mapping levee control gates (buried in the levee) 


> On Mar 22, 2017, at 9:42 PM, Greg Troxel <gdt at lexort.com> wrote:
> Also, presumably emergency spillways are mapped as areas, rather than
> lines,

What is interesting to me is that dykes (levees) are mapped as ways, though they can easily be mapped as areas. The levees around this system, about 10-15m tall and 40m wide are easily mappable from imagery and often have multiple ways that sit halfway up, on top, and transverse it, often all at once. 

If the minimum acceptable use is the way drawn on top of the levee, then there should be a tag similar to "riverbank" to map the extent of the levee to the sides. 

Maybe people are familiar with smaller dykes/levees, but I have never seen an entire 300km river system entirely encased in 10m levees before. And they are thinking of making the ones near the Tokyo Metro Area 20m. Mapping the area that such man-made structures extend from center seems like a no-brainer. 

I think the same would be true for a spillway - where the "top" of the spillway is, similar to the dyke tag, is probably the most important info, then it's area. 

Finally, wrapping up this tagging, of this levee system, there are hundreds of automatic/manual water control gates less than 1 meter wide to let streams and drains into the levee. There are about 100 larger 2-4m gates for larger streams and small rivers. 

Most of these small&medium sized ones are buried in the dyke/levee, and the control structure built out from the side of the levee, sometimes with a little building on top to protect the mechanism for lowering/raising the gate, is a common occurrence. How would I tag such a feature? They are easily seen on aerial imagery.

The white structure is built to stabilize the control structure sticking up. The gate is buried in the levee and the exit can be seen near the water. The structure above is easily seen (some kind of building or man_made tag), and the valve/gate structure below  is easily mapped as a node on the waterway. There are hundreds and hundreds of these gates. 


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