This article specifies that a connector is included when the following criteria are met:
- When connector is part of a network that is represented as being connected.
- When there is a gap with no collected network feature object between pieces of the network; for example, at a 2-dimensional (polygon) dam/weir that causes a gap between an upstream lake/pond and a downstream stream/river.
It gives an example of a connector going through a dam in order to connect the artificial path going through Lake Oroville with the Feather River downstream. Apparently we’ve done two better by mapping the tailrace tunnels, though the wiki recommends tagging such connections as waterway=pressurized to avoid counterintuitive rendering.
This looks like basically a big fixme=geometry: NHD knows the pond connects to Island Lake but doesn’t know the precise path by which the water flows. I wonder if natural subterranean rivers are modeled similarly – those definitely should be in the database.
This is like saying no one uses OSM for transportation analysis. Certainly there are more authoritative sources out there, but there are reasons for conducting more casual analyses too. For example, Waterway Map (discussion) segments OSM’s hydrologic features into color-coded watersheds for QA purposes, and River Runner depends on waterways to route a drop of water from any location to the ocean. It’s all for fun, but this is how OSM got its start as a major source for transportation data too.