> On Jun 5, 2019, at 10:54 AM, Joseph Eisenberg <joseph.eisenb...@gmail.com> > wrote: > > 75% of waterway=drain are 2m wide or less, so most mappers do not use > this tag for wide, canal-sized drainage waterways.
I tried repairing the mapping for an irrigation drain in my area to see how to map it. Similar to how streams and rivers often have weirs to control flow and overflow when they meet or split, small drains, especially irrigation, use “flash boards” to control flow. they fit into the body of drain channel and block the flow to raise the water level in the drain to supply water to additional ways. Larger drains have small structures (1-3m) that hold multiple sets of flash boards to control water level and flow to branching drains and ditches, and inadvertently act as a garbage trap. https://www.openstreetmap.org/way/696049197#map=19/36.42661/139.25801 <https://www.openstreetmap.org/way/696049197#map=19/36.42661/139.25801> This is a ~2x3m box of this nature. similar to flow_control=sluice_gate, I think I am going to use flow_control=flash_boards on drains/ditches with flash_boards controlling water flow and flow_control=flash_board_box on areas for the larger mappable enclosures visible in imagery for irrigation. Similar to the mapping the logical control of roads (stop signs, lights, barriers, etc), I imagine if people want to map the logical flow of this water, the restriction and flow features need to be defined beyond the flow. even if mapping them (for the most part) is not necessary for most people. we have dams and weirs for larger objects, and the flow_control key proposal for more man_made water controlling objects. Javbw
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