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Public-images-osm logo.svg usage = spillway
Llyn Brianne spillway.jpg
Specific waterway usage allowing the controlled release of water from a waterbody (reservoir, canal, river) Edit or translate this description.
Group: Waterways
Used on these elements
should not be used on nodesmay be used on waysmay be used on areasshould not be used on relations
Useful combination
Status: approvedPage for proposal


An artificial structure channeling water which allows it release from a water body, either under controlled circumstances or as a means of ensuring that water levels do not overtop and destroy containing structures (dams, levees). Spillways will normally be free of water but remains dangerous since it can be expected at any time.

Spillways may be in regular use or designed only to be used in emergencies.

How to Map

See waterway=river for common guidelines on how mapping waterways.

All spillways can be drawn as way way and tagged with waterway=canal + usage=spillway.
Larger ones can be completed with an area area and tagged with natural=water + water=canal + usage=spillway.

As any waterway, spillways should connect to the water body which it drains and to the downstream outlet.

The material=* of the spillway should be added.
The recent near collapse of the [W] Oroville Dam was in part precipitated because the emergency spillway was largely earth.

Wikipedia mentions different types of spillways, use spillway:type=* to describe these.

Related tags

Possible tagging mistakes

If you know places with this tag, verify if it could be tagged with another tag.
Automated edits are strongly discouraged unless you really know what you are doing!

See also