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Freshwater Wetlands Mapping

The Freshwater Wetlands Act (Article 24 of the Environmental Conservation Law) requires DEC and the Adirondack Park Agency (for areas inside the Adirondack Park) to map the freshwater wetlands that are subject to jurisdiction of the law. The law requires the maps to show "the approximate location of the actual wetland boundary." DEC will refine that approximate boundary by doing a field delineation for landowners when they need more precise information, such as when they are planning to work near a wetland area.

How Wetlands are Mapped

Wetlands are mapped using a variety of information sources, such as various types and seasons of aerial photography, soil surveys, elevational data, other wetlands inventories, and field verification. The wetlands are shown on 1:24,000 scale maps along with roads, streams and waterbodies, and other features. DEC then provides public notice. This includes distributing a set of draft wetland maps to appropriate local government clerks; sending letters by certified mail to affected landowners and local governments; publishing a legal notice in two newspapers; and publishing notice in the DEC Environmental Notice Bulletin. A public comment period is provided to receive comments on the accuracy of the maps, and follow-up field visits are conducted to ensure the accuracy of the maps. After these steps have been completed, the maps are finalized and copies of the maps are filed with the local government clerks. Notice of the completion of the map amendment process is provided to landowners, local governments and newspapers.

For most counties, the original wetland maps were completed and filed between 1984 and 1986. Filed maps exist for all counties except for the portions of these six counties located within the Adirondack Park: Franklin, Fulton, Herkimer, Saratoga, St. Lawrence, and Washington. In addition, the wetland maps have been amended at various locations to correct errors and to reflect changes in the wetlands resource. The Freshwater Wetlands Statistics Chart (PDF) (46 KB) shows amendment dates and wetland acreage by county.

Wetland Map Amendments

Wetlands are a changing natural resource and their boundaries often change over time. Sometimes, the boundary changes are minor so the maps do not need to be amended. However, when boundaries change substantially, which can happen over longer periods of time, the maps need to be revised to accurately reflect the new wetland boundary.

Wetland maps can be inaccurate for other reasons, as well. Improved technology has given us the ability to detect wetlands that were missed when the original wetlands mapping work was done in the 1980s. Using new and better aerial photography, computer based geographic information system capabilities and digital soil surveys, biologists are able to inventory wetlands that meet the legal definition of wetland, but are not shown on the regulatory maps.

The science of wetlands also has matured in the past 20 years. The old perception that all wetlands are marshy and have open water has been placed in a new context. We now know that only about 14% of our wetlands fit this cattail-marsh-with-a-duck image. Most of our wetlands are shrub or forested swamps, and many lie along rivers and streams in the floodplain riparian zone. In the past, many of these critical wetlands were missed in the mapping process.

Finally, amendments might occur when technical corrections to the maps are needed. These may include renumbering wetlands, correcting notification deficiencies, changing wetland classifications, and updating symbols. Typically, amendments are not undertaken solely to do technical changes; these most often are included as part of other resource-based amendments.

Map amendments may consist of adding entirely new wetlands; adjusting the boundaries of existing mapped wetlands; deleting areas that no longer meet the statutory definition of wetland, either because they are too small or do not support wetland vegetation; extending the regulated adjacent area of the wetland beyond 100 feet (measured perpendicular to the wetland) which may be needed to protect the integrity of the wetland; or making other technical changes to the maps. Amendments range from a single amendment on one wetland map to a comprehensive re-mapping of entire wetland map or counties. Wetland map amendments have been done in many counties around the state.

An amendment is officially started when notice of the wetland map amendments is provided to landowners, the public, and local officials in the same manner as that required for the original wetlands maps (See How Wetlands are Mapped) Once an amendment has been officially begun, the wetland(s) subject to the amendment become regulated and the property owners are required to obtain a permit to conduct regulated activity in that wetland(s).

There is more information about wetland map amendments underway and completed map amendments (PDF)(24 KB).

What The Wetland Maps Show

The NYS Article 24 Freshwater Wetland maps show the approximate location of the wetland boundary and the unique alpha-numeric (e.g. AB-12) wetland identification number assigned to each wetland. The maps show roads and hydrography (such as steams and ponds), but do not show the regulated wetland adjacent area nor the wetland classifications. Also, they do not show the topography, contours, or elevational data.

Because of the scale of the map and aerial photography used to produce the wetland boundaries, an on-site field delineation is often necessary to determine the actual location of the wetland on the ground. Interested landowners can contact the DEC Regional Office where the wetland is located if a delineation is needed.

Where To View The Wetland Maps

The following online mapping options can be used to view the current regulatory wetland boundary which includes amendments underway. In addition, maps of amendments underway are usually available

Paper maps of the filed maps and amendments underway are available at these locations for wetlands within their jurisdiction:

  • DEC Regional Offices
  • Clerk's office for each county, city, town and village
  • Adirondack Park Wetland Maps can be viewed at the Adirondack Park Agency 518-891-4050

Where To Get Wetland Maps

Where to Get Wetland Maps

DEC regional office staff and many local government clerks are willing to photocopy portions of wetlands maps for interested parties. This includes portions of filed maps as well as wetland amendment maps. Contact the County, City, Town, and Village Clerk's offices for the area where the wetlands are located.

If paper copies of full size wetland maps are needed, they must be ordered. Wetland amendment maps are available for larger scale or county wide amendments These maps can be ordered from the Syracuse Blue Print Company. Order forms are available at all DEC Region Offices. Wetland maps are produced by county hence only the portion of the county that is located on a given quadrangle map will appear on that county's wetland maps. In order to get complete quadrangle coverage, it is necessary to purchase the number of quadrangle maps that represent the number of counties on that quadrangle map.

How to Obtain Digital Wetlands Data

Digital wetlands boundary data are available for the wetlands outside the Adirondack Park. These data represent the current regulatory wetland boundaries which includes amendments underway. These data represent the boundaries, associated wetland identification numbers and classification codes. No other wetland map information is included. These data are available at no cost from the Cornell University Geospatial Information Repository (CUGIR).

The digital wetlands boundary data are provided for GIS resource analysis at scales equal to the 1:24,000 scale of original mapping or smaller scales (e.g., 1:100,000 scale). Additional data layers are needed in order to visualize roads, streams, political borders and other features found on an official NYS DEC Article 24 Freshwater Wetlands map. Possible sources for the additional data include CUGIR and the New York State GIS Clearinghouse.

Other Wetland Maps

National Wetland Inventory (NWI) Maps

The National Wetlands Inventory (NWI) maps are produced by the U.S. Fish and Wildlife Service (USFWS). The NWI maps contain information on the location and characteristics of wetlands and deepwater habitats. Wetlands are classified using the method described in the Classification of Wetlands and Deepwater Habitats of the United States, published by the U.S. Fish & Wildlife Service. The National Wetlands Inventory appears on 1:24,000 U.S. Geological Survey (USGS) base maps.

Paper NWI maps can be ordered from the Cornell University Institute for Resource Information Sciences (IRIS) webpage, or by contacting the IRIS NWI Program at 607-255-6520.

The NWI digital data can be downloaded from the U.S. Fish and Wildlife Service. NWI wetlands can be viewed using the Wetland Mapper on the USFWS website.


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