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Short Citation:
Office for Coastal Management, 2023: Coastal Wetlands,

Item Identification

Title: Coastal Wetlands
Status: Completed
Publication Date: 2023-07-21

This data set represents the extent, approximate location and type of estuarine and marine wetland habitats in the United States and its Territories. These data delineate the areal extent of wetlands and surface waters as defined by Cowardin et al. (1979), which represents a biological definition of wetlands and deepwater habitats. There is no attempt to define the limits of proprietary jurisdiction of any Federal, State, or local government, or to establish the geographical scope of the regulatory programs of government agencies. Some wetland habitats may be under represented or excluded in certain areas because of the limitations of aerial imagery as the primary data source used to detect wetlands. These habitats include seagrasses or submerged aquatic vegetation that are found in the intertidal and subtidal zones of estuaries and near shore coastal waters and also some deepwater reef communities (coral or tuberficid worm reefs). These habitats, because of their depth and water clarity, go undetected by most aerial imagery. By policy, the Service also excludes certain types of "farmed wetlands" as may be defined by the Food Security Act or that do not coincide with the Cowardin et al. definition. Contact the Service's Regional Wetland Coordinator for additional information on what types of farmed wetlands are included on wetland maps. This dataset should be used in conjunction with the Wetlands_Project_Metadata layer, which contains project boundaries, specific wetlands mapping procedures and information on dates, scales and emulsion of imagery used to map the wetlands within specific project boundaries.


To support ocean planning activities pursuant to the Executive Order Regarding the Ocean Policy to Advance the Economic, Security, and Environmental Interests of the United States, the Energy Policy Act, the National Environmental Policy Act, the Rivers and Harbors Act, and the Coastal Zone Management Act.

Supplemental Information:

Bureau Code: 006:48, Program Code: 006:055


Theme Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Science Keywords
Global Change Master Directory (GCMD) Science Keywords
ISO 19115 Topic Category

Spatial Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Location Keywords
None Exclusive Economic Zone
None Outer Continental Shelf
None Territorial Sea
None United States of America

Physical Location

Organization: Office for Coastal Management
City: Charleston
State/Province: SC

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: None Planned
Data Presentation Form: Map (digital)
Entity Attribute Overview:

NWICode, stateName, aquaticSetting, NMWIClass, NWIClass2, NWISubclass, NWISubclass2, NWIWaterRegime, specialModifier, salinityRegime, salinityCode, biotic, bioticCode, substrate, substrateCode

Distribution Liability:

Data Set Credit: U.S. Fish and Wildlife Service

Support Roles

Point of Contact

CC ID: 698201
Date Effective From: 2017-11-29
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


Currentness Reference: Publication Date

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 698199
W° Bound: -170.847065
E° Bound: 145.830768
N° Bound: 71.390922
S° Bound: -14.373719

Extent Group 1 / Time Frame 1

CC ID: 698198
Time Frame Type: Discrete
Start: 2017-12

Spatial Information

Spatial Representation

Representations Used

Grid: No
Vector: Yes
Text / Table: No
Stereo Model: No
Video: No

Reference Systems

Reference System 1

CC ID: 1261300

Coordinate Reference System

CRS Type: Geographic 2D
EPSG Code: EPSG:4269
EPSG Name: NAD83
See Full Coordinate Reference System Information

Access Information

Security Class: Unclassified
Data Use Constraints:

For coastal and ocean planning

Distribution Information

Distribution 1

CC ID: 698207
Download URL:

Data Quality


Please see source data documentation

Completeness Report:


Conceptual Consistency:

These data are logically consistent




CC ID: 698215
Contact Role Type: Originator
Contact Type: Organization
Contact Name: U.S. Fish and Wildlife Service
Publish Date: 2021-07-02
Extent Type: Discrete
Extent Start Date/Time: 2021
Citation URL:

Process Steps

Process Step 1

CC ID: 1262028

Data Download, Preparation, and Filtering

Data was downloaded from the NWI ( for each state encompassing the coastal United States. Data for a total of 25 states were downloaded. Each File Geodatabase of raw data from NWI inherently contains 4 feature classes including all wetlands data for that state, historical mapping information, metadata documentation as spatial data describing data compilation information for different regions, or projects within a state, and a dataset extent boundary.

The NWI feature class containing wetlands data was extracted for each state and reviewed separately for each step of the data preparation process, until final data compilation.

A number of the raw datasets contained errors within the spatial index. The spatial index for every dataset was reset as an initial processing step.

Coastal wetlands included in this dataset were defined by the NWI classification codes of system Marine (M) and system Estuarine (E). All sub-classifications below these two systems were included. Other systems were excluded from the coastal wetlands dataset.

In order to accommodate XY tolerances in meters as part of the geometry review, filtered data was projected to North_America_Albers_Equal_Area_Conic, EPSG 102008. This projection also ensured adherence to the NOAA standard of using GRS_1980.

Prepared data was saved in a new File Geodatabase, as a feature dataset by state. Data was stored as such in order to build topology as part of the geometry review.

Process Date/Time: 2021-12-22 00:00:00

Process Step 2

CC ID: 1262029

Geometry Review

Topology was built within ArcGIS Pro version 2.8.3 for each state feature dataset separately, in order to identify and repair errors.

A series of tests was conducted to determine the optimal topology XY resolution parameter. Generally, this parameter should be no less than 0.001 meters. It was determined that resolutions tested that were greater than 0.1 meters (0.5 meters, 1 meter, 4 meters) significantly altered the data when validated. A resolution of 0.1 meters was found to be optimal for these data and used consistently across all project topologies.

Appropriate topologic rules for evaluating a single polygon dataset were applied to all state datasets. These rules were a) features must not overlap, and b) features must not contain gaps. Errors were then evaluated and repaired.

All overlaps were removed across all states.

A large number of gaps were identified for each state, as any portion of a feature that did not touch another feature was identified as a gap. Non-adjacent features are inherently a valid part of NWI wetlands, and are permitted, however smaller gaps and slivers as errors do also exist. Assessment of gaps was conducted initially to mark the vast majority of the large gaps as exceptions. This allowed smaller, gap errors to be more visible. Gap errors were scanned at a scale of 1:12,000 and fixed where possible. Given the number of errors and the scope of this project, best efforts to resolve gap errors were made, but some remain in the final data compilation.

Self-intersecting polygons are another geometry error that was assessed. These are instances where a single polygon intersects itself.

Checks for these geometry errors was first conducted using the ESRI Check Geometry and Repair Geometry tools and the ESRI validation rule. The OGC validation rule was evaluated, but not used in all cases, as it requires that no non-linear features exist. Non-linear features do exist in NWI data, and eliminating these features resulted in drastic changes to the raw data, causing additional overlapping polygons, gaps, and slivers. It was determined that conducting Check Geometry with the OGC validation rule resulted in more errors than it resolved, and under the scope of this project additional clean-up to mitigate these created errors was not possible.

QGIS software was also used to locate self-intersecting polygons by checking validation. The GEOS option was set to on, and the option to Ignore Ring Self Intersections was not checked.

Errors were identified in QGIS, but resolved in ArcGIS Pro. Given the magnitude of the number of these errors best efforts were made to clean up the majority of errors, however some still remain.

Finally, the extent of the feature class was reset using the ArcGIS Pro function, RecalculateFeatureClassExtent

Process Date/Time: 2021-12-22 00:00:00

Process Step 3

CC ID: 1262030


Attribution was based on information in the NWI classification scheme. NWI classifications were also cross-walked with CMECS codes, and these coded domains and descriptions were also included in the attribution.

The raw NWI data contains a field titled ATTRIBUTE that defines the NWI classification code. These alphanumeric classification codes correspond to nomenclature, defined by NWI, that best describes a particular wetland habitat. NWI provides a lookup table for each code that defines each portion of the classification code.

Attribution was applied to the coastal wetlands dataset that broke out each classification code and described the system, subsystem, class, subclass, and any modifiers including water regime, special modifiers, water chemistry, and soil for each wetland feature. These definitions were derived directly from NWI. Wetland classifications were broadly reviewed, and in some cases suggested edits were provided by NOAA OCM to fix incorrect classifications.

A crosswalk of NWI classification codes and CMECS codes was provided by NOAA OCM. This crosswalk was used to define the CMECS biotic definition, biotic code, substrate definition, and substrate code for each wetland feature.

Process Date/Time: 2021-12-22 00:00:00

Process Step 4

CC ID: 1262031

Data Compilation

Following geometry review and attribution, projects were merged together based on region. Regions include: the Atlantic coast, the Gulf coast, the Pacific coast, Alaska, and U.S. territories and islands. Data was compiled at these scales instead of the national scale to make viewing and using the data more manageable.

Adjacent NWI state datasets overlap each other. Overlapping state datasets share identical features except at the boundaries of the dataset, where features are cut-off at a hard boundary line. For this reason, adjacent state datasets could not simply be merged together, as merged products would contain duplicate and overlapping non-identical features. This overlapping needed to be handled first:

Using state dataset extents overlapping data between states was clipped out of neighboring datasets. State datasets were then merged together and it was confirmed that data along the created stitch line met perfectly without overlaps or gaps created. Data between the now adjacent, but not overlapping, state datasets were merged together to create a single polygon spanning both state datasets where applicable. In instances where NWI classifications differed between adjacent polygons, the differentiation between the polygons remained.

Process Date/Time: 2021-12-22 00:00:00

Process Step 5

CC ID: 1262032

Data Integration and Tuning

All regions were projected to NAD83

All regions were combined using the ArcGIS Pro function MERGE

The estuarine and marine subtidal features were removed

Field size settings were reduced to approximate field size values

The ArcGIS Pro function REPAIR GEOMETRY with the OGC parameter was executed

The ArcGIS Pro functions RECALCULATE FEATURE CLASS EXTENT was executed

Process Date/Time: 2023-07-21 00:00:00

Child Items

Rubric scores updated every 15m

Rubric Score Type Title
Entity Coastal Wetlands

Catalog Details

Catalog Item ID: 50447
GUID: gov.noaa.nmfs.inport:50447
Metadata Record Created By: Anna Verrill
Metadata Record Created: 2017-11-29 15:26+0000
Metadata Record Last Modified By: Daniel Martin
Metadata Record Last Modified: 2023-07-24 12:34+0000
Metadata Record Published: 2017-12-07
Owner Org: OCM
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2017-12-07
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2018-12-07