Tag:waterway=weir
 waterway = weir
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A barrier built across a river to control water speed and depth. Water can still flow over the top.  
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| Rendering in openstreetmap-carto |
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| Group: Waterways |
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| Useful combination |
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| Wikidata |
| Q1066997 |
Status: approved
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A barrier built across a river, sometimes to divert water for industrial purposes. Water can still flow over the top. In the US this is often called a low-head or low-rise dam.
How to map
To map a small weir add a node along a river and tag it waterway=weir. If the weir has a name tag it name=*.
If the weir is long enough to be mapped as a way, create a way along the length of the weir and tag it waterway=weir. Again, add a name=* if it is known. The waterway=weir should share a node with the river where they cross. Like a natural=cliff the line direction matters: On the left side there is the high side, on the right side is the lower side.
Sometimes a fish pass is related with the weir.
(High-)ways over a weir
This subject was not part of the proposal but the most straightforward solution is that the highway=* and waterway=weir share a way. A section of this way may be marked with ford=yes if there is a ford.
Validators and QA tools may complain about this combination because they may have an overly generic rule saying that highways and waterways can not share a single way - this is one of the valid exceptions and tools should be fixed to accept it.
Rendering
| Type | Picture | Tags | Mapnik |
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 node
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waterway=weir | 
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 way
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waterway=weir | 
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