Who mapped these? In New Mexico we have a ton of dry arroyos that maybe have a couple inches of flowing water a few times a year. Zooming in at places I'm familiar with, a surprising number of them are mapped. I know of rez roads[1] nearby that aren't on OSM or any map I know of, but the ditch we used for cross country practice is. Wild!
[1] Two-track dirt roads on the Navajo Reservation that are not regularly maintained, or officially numbered/named but which are actively used.
Thanks, that is helpful. It looks like for some of the larger ones the editors left comments that dataset was imported from USGS quads which makes sense, while other smaller ones don't list any source information - possibly mapped personally by hiking with a GPS?
I added a set of arroyos in New Mexico using USGS quadrangle sheets, which originate from digital elevation models and ground surveys in the 1980s. They're tagged as "intermittent streams" in OSM. There's a lot more work to do outside the national forests and major cities. One thing I noticed is that the dry beds shape road and settlement patterns, beyond just being useful for navigation.
NM is undermapped relative to other states. I've wondered if this has to do with the complex governance and land claims (which can make it difficult to do bulk data imports).
Sometimes waterway maps include calculated flowlines. These are algorithmically derived from digital elevation data and more accurately represent where water would flow were there water flowing. That's really important not just for New Mexico arroyos but for most of the surface of the earth; there are a lot more flowlines than perennial streams.
I don't know the provenance of this data though. It's pretty spotty, I don't think someone just imported the NHD flowlines dataset or something.
I'm in Thailand, and zooming in to places I'm familiar with, a surprising number of rivers and waterfalls are completely missing. I suppose there are quite a few factors that affect data quality in different regions around the world.
I'm in New Mexico too, there's some creeks I frequent that are considered "navigable waterways" and unless it's monsoon season, you barely get your ankles wet lol.
[1] Two-track dirt roads on the Navajo Reservation that are not regularly maintained, or officially numbered/named but which are actively used.