False positive finding on wash trails

[zelonewolf@…]

In certain areas, such as the western United States, it is common to find dry riverbeds which only run with water when it rains. These are known as "washes" When it is not raining, some of these dry washes are used as paths or as track roads. Below is one such example:

​https://www.openstreetmap.org/way/6143573

In this case, the validator flags a "suspicious tag combination" finding for "highway with waterway".

These objects should be valid both as paths and as intermittent streams. There is no need for the validator to recommend that users create separate overlapping ways for the same object.

This validation finding should be suppressed for the following combinations:

waterway=stream + intermittent=yes + highway=track
waterway=stream + intermittent=yes + highway=path

[skyper]

Two primary tags on one object will often cause problems. Not sure where to start here. Is it better to use a different highway value as indicator or is an additional secondary tag enough? How is this solved with ice_roads on rivers?

[anonymous]

As I understand it, ice_roads is a separate key that can get added to a road that is only usable in the winter. I'm not aware of a tag that means "when it rains, this trail becomes a river".

The obvious fix for the validator's recommendation is to create two separate ways, one for the path, and one for the intermittent stream. This would cause the mapper to have two separate OSM objects for the same feature (violating the one object, one feature rule). Even though some will find a combination of the highway and waterway keys to be icky, a way tagged as an intermittent stream AND a path has clear semantic meaning (though would be clearly wrong for a non-intermittent stream).

I do realize this is an unusual corner case, but I have encountered these objects in the wild and I'm not quite sure whether I should model these features differently.

[skyper]

No, I understand, that in this case both primary tags should be at the same object though I think we need an additional tag to mark this situation and to help software like routers and QA.

How about ​ice_road=yes and ​flood_prone=yes as secondary tags to trigger an exclusion from this test. Do we need another tag for washes or does flood_prone=yes work?