National Wetlands Inventory

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Much like the National Hydrography Dataset, The National Wetland Inventory (NWI) is a United States-wide hydrography dataset produced by the US Fish and Wildlife Service (USFWS). This dataset includes primarily wetland features like marsh, saltmarsh, bog, and swamp, but also natural water features: lakes and ponds. Conflicts should be avoided with the National Hydrography Dataset which also contains mapping of water features.

Getting the data

Data can be downloaded by statewide or HUC8 watershed extent (recommended) at the [Wetlands Mapper] or accessed through the [Data Download] page.

Attributes to OSM tags

The following has been borrowed from the Maryland/Wetlands Import page:

The attribution of the data is based on published Classification of Wetlands and Deepwater Habitats of the United States (2013, PDF) based on the de facto standard published by Cowardin et al in 1979. The Cowardin system is the federal standard for wetland classification used in the National Wetlands Inventory. The system uses an alphanumeric code to represent a wetlands characteristics. The codes are concatenated into a single string and are sometimes nested with other classifications. While useful for wetland inventory and research, the 500+ classification possibilities are outside of the scope of usefulness for the OpenStreetMap project (which has around ten wetland classifications in common use).

It is necessary to generalize the classifications for OSM. The United States Fish and Wildlife Service has a simple classification scheme that is based on the first few characters of the full Cowardin classification code, that this project will replicate.

The following table shows the generalized Cowardin wetland types and their OSM equivalent.

Wetland type Map-
Code
cowardin:description wetland:description OSM tags
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

See also