Tag:waterway=flowline

The tag waterway=flowline can be used to map the slow-moving flow of water through a lake, reservoir, or other large water body.

Background

To fully model the flow of water over a landmass, all streams and rivers features need to be connected from source to outlet without interruption. Watercourses often flow through lakes and reservoirs, presenting a data problem. Historically, some mappers have omitted a waterway=* through lakes, leaving the network incomplete. Other mappers have used waterway=river or waterway=stream to model the flow, but watercourses are appreciably different from lake flow. It can take years for water to cycle through a lake. waterway=flowline is intended for this special case.

How to map

Where a watercourse enters a lake and ceases to be recognizable as a stream or river, start a way tagged waterway=flowline. Draw the flowline along the centerline of the lake towards the outlet(s), i.e. in the general downstream direction. (Do not attempt to model the exact fluid dynamics in the lake.) Connect the flowline to the start point of the steam or river that exits the lake.

Smaller tributaries entering the lake can also be modeled as waterway=flowline, drawn from the outlet on the edge of the lake to the central flowline. Model the flow around large islands by adding one flowline for each channel, similar to mapping rivers around river islands.

Useful combinations

• intermittent=* – does it periodically run dry
• tidal=* – is it affected by tides
• waterbody:name=* – the name of the containing body of water
• boat=* – boat access
  • canoe=* – canoe and kayak access
  • motorboat=* – motor-powered boat access
  • sailboat=* – sail-powered boat access
• oneway:boat=* – if boats are able to travel in both directions (defaults to oneway:boat=no)

The tag implies rapids=no. If a feature has rapids it's probably not a flowline.

Examples

• 1214889931 1214889931 – Cayuga Lake central flowline
• 1248250769 1248250769 – Delaware Bay central flowline
• 1243063035 1243063035 – Lake Champlain tributary flowline

See also

• waterway=link – virtual topological connections, e.g. between a water body's centerline (or flow line) and an access point on land, in order to enable watercraft or multi-modal routing.
• seamark:type=fairway