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Comment by pavon | Hacker News Reader

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.

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In the USA, this is likely sourced from the National Hydrography Dataset:

https://www.usgs.gov/national-hydrography/national-hydrograp...

Nope, it's 100% OpenStreetMap data.

(I made WaterwayMap.org)

OSM has some NHD imports.

You can go to https://openstreetmap.org/ , zoom in and enable the map data layer. History is accessible from the object pages.

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 know I personally mapped one with a GPS and canoe.

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.

It is from OpenStreetMap. (see header and footer.) You can fix any errors you see!

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.

Add them in https://rapideditor.org/rapid

There are usually several satellite image providers for anywhere that isn't a sea or ocean. You can trace over them.

Asia has much lower number of OpenStreetMap editors than say Europe.

Help is welcome! See https://www.openstreetmap.org

> dry arroyos that maybe have a couple inches of flowing water a few times a year

As you can see they are tagged as 'intermittent'. https://www.openstreetmap.org/way/380234870

Yes, sorry I didn't mean to imply that they were incorrect or shouldn't be mapped. I was just pleasantly surprised that someone had done that work.

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.

By the legal standards that I understand to apply, “navigable waterway” is any waterway that is, or could be made, navigable. So it doesn’t take much.

“Who mapped these?” All the data is from OpenStreetMap!

_(I made WaterwayMap.org)_

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