Carteret County, NC - Wetland import

Hi everyone,

I’ve been working on & off on this project for a couple of years, but now I really want to get it done with that, so here I am writing in this community about my project to import Wetland ARCGIS Data for the Carteret County in North Carolina.


The reason why I decided this area of the USA is because it’s my favorite place to travel and I wanted to get more accuracy on the map. It started by simply improving some of the existing shapes, but I found out that the county has a great GIS service with a lot of data for the Wetland.
Wetlands | Carteret County Open GIS Data Site (

Steps taken

Back in 2021, I wrote to them about those datas and they were ok for me to use them in OpenStreetMap since the data are Open to the public. I didn’t get a proper approval at this time, but it’s something I will do before starting the importation.

The accuracy difference from the current data is massive.

Where I am right now

Right now I’m making sure I’m using the appropriate tags, deleting some of the source’s tags that aren’t relevant to OSM and I need to do a little bit of cleanup and delete useless shapes and shapes I’m not sure what it is. Some tags are irrelevant, but sometime it can be used by boats to know where it’s more shallow.

Currently I have a mix of tidal flat, shoal, bogs, swamp and almost everything related to wetland.

I’m using JOSM and I will import one little area at a time to not make mistakes. I will do that by merging my new shapes with the current one (if there is an existing one).

What I need to do

  • Getting a proper approval to use the data (even if they didn’t rejected me when I wrote I wanted to use their data for OSM). Is this “term and condition” page enough? GIS Terms and Conditions (
  • Create an import account
  • Create a wiki page
  • Start importing

Thank you very much.

1 Like

This looks like an noble and valient effort to improve what can be a challenging and daunting task to map manually. An entire scientific area of study exists around the classification and delineation of wetlands. Why reinvent the wheel is how I’d approach an import like this one. An expert has already delineated the data, so I say have at it.

Some years ago I began a similar import and although it was not finished, I think you would find some utility in the tagging research I had come up with. If you are successful here, I may be inspired to resume my work!

Most useful, I think, would be the conversion of the Cowardin wetland classification system to the OSM wetland tagging structure. I propose the following based on the ATTRIBUTE attribute in your dataset:

Wetland Type MapCode cowardin:description wetland:description OSM Natural OSM Detail 1
Estuarine Deepwater E1 Estuarine subtidal water and wetland Open water estuary, bay, sound, open ocean natural=water tidal=yes
Marine Deepwater M1 Marine subtidal water and wetland Open water estuary, bay, sound, open ocean natural=water tidal=yes
Estuarine wetland E2 Estuarine intertidal wetland Vegetated and non-vegetated brackish and saltwater marsh, shrubs, beach, bar, shoal or flat natural=wetland wetland=saltmarsh
Marine wetland M2 Marine intertidal wetland Vegetated and non-vegetated brackish and saltwater marsh, shrubs, beach, bar, shoal or flat natural=wetland wetland=saltmarsh
Lakes L Lacustrine wetland and deepwater Lake or reservoir basin natural=water water=lake
Freshwater Emergent wetland PEM Palustrine emergent Herbaceous march, fen, swale and wet meadow natural=wetland wetland=marsh
Freshwater Shrub wetland PSS Palustrine shrub Forested swamp or wetland shrub bog or wetland natural=wetland wetland=bog
Freshwater Forested wetland PFO Palustrine forested Forested swamp or wetland shrub bog or wetland natural=wetland wetland=swamp
Freshwater pond PUB Palustrine unconsolidated bottom Pond natural=water water=pond
Freshwater pond PAB Palustrine aquatic bed Pond natural=water water=pond
Riverine R Riverine wetland and deepwater River or stream channel natural=water water=pond

In addition to the reclassification, I would advocate for preserving the ATTRIBUTE tag as a new tag we could invent. Something like, wetland:cowardin=*.

According to the above:
“This data is subset of the USFWS Natl Wetlands Inventory.”

Which means you could go directly to USFSW and get the data and not have to worry about the license as USFWS data is public domain.

Just because there is more data, doesn’t mean it is more accurate. It might be, but we shouldn’t assume so. I would be interested in an actual assesment of its accuracy.

That is very important. It is important not to wholesale wipe out existing data and replace it with this data. For one thing, the existing data may have some tagging that the new data does not. e.g. the name of a wetland. We also want to preserve the history of the objects currently in the OSM database when appropriate. In JOSM you can use the replace geometry function to preserve the history.

Your table is very helpful, because I was using a similar one, but without the OSM equivalent, so it was mostly me trying to figure out which code means what.

I’m using a different file that I don’t remember where I found it.

E2EM5 is wetland=reedbed

For E2 and M2, should it be best to also use tidal=yes since it can be flooded on high tide?

I’m also concerned about some others like:

  • Should E1 be wetland=tidalflat ?
  • E2SS which are shrub and small plants. Is it sill saltmarsh?

Thank you!

The data found on the USFWS website here National Wetlands Inventory ( is taking a much larger surface area, but most shapes from this one and Carteret county GIS are the the same. I think USFWS is adding docks, E1 and some more details, but they are generally the same.

In my example above, I used the 2021 data which included docks area and E1, but it looks like they removed them from the 2022 update.

They also have the ditches from the farm land up north, but I they are already in OSM, so I not do anything with them.

I will concentrate on the things that aren’t already there, update/merge current shapes and delete the ones that are not relevant anymore.

But the most difficult will be those parts

They are tagged E2USM so maybe wetland=tidalflat

The USFWS is also adding another part here

E1ABL which may be irrelevant for OSM. Not too sure about this one. I may only work with what’s on the Carteret County GIS which may make my work easier.

I will also simplify the ways and shapes for OSM, because some are too detailed.

Tidalflat works for those submerged ones. Underwater mapping in OSM is not well established. You could review those manually and decide to delete if they’re usually fully submerged.