Wetland Classification Codes

The wetland classification codes are a series of letter and number codes that have been developed to adapt the national wetland classification system to map form. These alpha-numeric codes correspond to the classification nomenclature that best describes a particular wetland habitat. For example, PFO1A = Palustrine (P), Forested (FO), Broad-leaved Deciduous (1), Temporarily Flooded (A).

To view full descriptions of wetland codes please visit the Wetlands Mapper. When a wetland polygon is clicked on, the option to view the complete code description is provided. This opens the description tab, which provides users with full details of the classification code for that wetland feature. To decode data in your own mapping environment, please refer to the Wetlands Code Definitions Download Package available below.

Wetlands Code Interpreter Tool Download

This Wetlands Decoder Tool runs in Python 3 and provides users with validation of acceptable wetland classification codes, as well as full Cowardin habitat descriptions.

Wetlands Code Interpreter - October 2023

Wetlands Code Interpreter.Zip

Wetlands Decoder Table Download

The database table in this download provides a crosswalk from U.S. Fish and Wildlife Service, National Wetlands Inventory (NWI) wetlands data, as defined by the Federal Wetland Mapping Standard, to the complete wetland definitions, as defined by the Federal Wetlands Classification Standard. The table can be joined with the NWI wetlands data using the 'Attribute' field. This will provide users with a full wetland or deepwater habitat description for each polygon. The NWI dataset and associated tables are updated on a biannual basis, typically in October and May. To ensure you have the most up to date information, please refer to the published date in the metadata, and download new data and tables regularly.

NWI Code Definitions Download Package - Last updated: October 2024

NWI Code Definitions.zip (Arc 10 Compatible)

Important Classification Documents

For more information about wetland codes and the wetland classification system please refer to the documents linked below.

Classification of Wetlands and Deepwater Habitats of the United States
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Classification of Wetlands and Deepwater Habitats of the United States

The Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al. 1979) was developed to support a detailed inventory and periodic monitoring of the Nation’s wet habitats using remote sensing. Often referred to as “The Cowardin System,” it is a hierarchical system that...

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National Wetland Inventory Wetlands and Deepwater Map Code Diagram
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National Wetland Inventory Wetlands and Deepwater Map Code Diagram

This diagram shows the hierarchy of the Wetlands and Deepwater Habitats classification system, from System to Subclass, and includes special modifiers. Water regimes are not included in this diagram.

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National Wetland Inventory Water Regime Restriction Table
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National Wetland Inventory Water Regime Restriction Table

This table provides guidance on which water regimes are allowed for each wetland system, subsystem, class, and/or subclass. This document should be used in conjunction with the NWI Map Code Diagram.

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Data Collection Requirements and Procedures for Mapping Wetland, Deepwater, and Related Habitats of the United States (version 3)
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Data Collection Requirements and Procedures for Mapping Wetland, Deepwater, and Related Habitats of the United States (version 3)

These technical procedures serve as a reference for conducting the image analysis work associated with mapping wetlands and deepwater habitats. This document is intended to be comprehensive, however situations may develop that require modifications or additions. This information is intended to...

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