• Wetland Maps in Wisconsin
• How Inventory Maps are Made
• Mapping Units
• Obtaining Wetland Maps
Wetland Maps in Wisconsin
In 1978, through statutory mandate, Wisconsin created the mapping program known as the Wisconsin Wetland Inventory (WWI), now managed by the
Wisconsin Department of Natural Resources (WisDNR). WWI is the basis for certain local zoning laws and is the only statewide assessment of wetlands. Other states' wetland maps are produced through the National Wetlands Inventory which was founded in 1977.
Wetlands mapping is considered a "foundational element" by the Wisconsin Land Information Program (WLIP), along with soil maps, parcel maps, zoning maps and other land information components. Because all of Wisconsin's 72 counties participate in the WLIP, they choose to allocate the program's funding to wetland mapping. To keep an accurate account of the state's wetlands, both their extent as well as their vegetative cover, wetland maps need to be updated at least every 10 years. But because of budget restraints to date, these maps have been updated on a 20 year cycle.
A convenient way to monitor wetlands is with digitized data. Digital data can be overlaid with other computerized resource data (in a GIS) to allow better management decisions through more efficient and effective access to information. Digital data is available for 28 of Wisconsin's counties and the process of digital conversion is continuing with funding from the WISCLAND Project.
The custodian of the WWI's maps and digital database is the WisDNR's Bureau of Water Regulation and Zoning (WRZ). See below to find out how to obtain wetland data and maps.
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How Inventory Maps are Made
The process by which inventory maps are made consists of four steps:
Aerial photography makes use of precision mapping cameras to take stereoscopic (overlapping) black and white infrared aerial photographs. Each photo covers a four square-mile area (four public land survey "sections") at a scale of 1"=1,667'.
• obtaining aerial photography
• photo interpretation
• map drafting
• digitizing map information
After photos are acquired, photo-interpreters use a stereoscope to view photo pairs in stereo, or in 3 dimensions. The infrared film emulsion enhances detection of tone, texture, reflectance, and pattern, enabling the interpreter to identify wetland vegetation types.
Interpreters also refer to other information sources: soil surveys, topographic maps, and previous wetland inventories. A representative sampling of areas are checked in the field for accuracy and consistency, as are any areas where photo analysis is inconclusive.
Wetland boundaries and classifications are drafted directly onto photogrammetric base maps at a scale of 1:24,000 (1"= 2,000'). There is one such map for each Public Land Survey System township. Other information is also noted, including municipal boundaries, waterways, and major highways.
The date a base map photo was taken may differ considerably from the date of the interpreted infrared photo. For example, information from a photograph taken in 1990 may be drafted on to a 1980 photographic base map. This can be confusing if landmarks have changed. Both dates must therefore be clearly labeled on maps.
The last step in producing Inventory maps is the conversion of paper maps to computer data (digitizing). Digitizing is accomplished by mounting maps on a digitizing table and tracing boundaries. Wetland boundaries and labels are then stored as digital computer data. Digital data can be used for complex analyses that may be inefficient or impossible using paper maps, and to analyze wetland loss on a county, state, or regional basis. Wetland data can be combined with automated information about floodplains, soils, transportation networks, etc., to create new generations of information.
While WWI maps are available for the entire state, digital versions of these maps are available only for parts of the state. The updating and
digitizing of full state coverage is an ongoing process. A long term goal is to use digital orthophoto quarter-quadrangles as a more fully-corrected base map upon which to register wetland delineations.
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Mapping Units Return to Top
Wetlands are distinguished from other land features with stereoscopic black and white infrared aerial photographs. Any wetland larger than
2 or 5 acres will be classified on Inventory Maps. A small wetland consisting of a couple of acres will have only one classification and
is considered one mapping unit. Larger wetlands may be subdivided into small mapping units. Because of land use changes, the classification
and boundaries of wetlands show ground conditions as of the date of the interpreted aerial photography. The DNR produces Inventory Maps on a
10 year cycle but because of budget constraints it is closer to a 20 year cycle. The updating process consists of interpretation of new aerial
photography and drafting current wetland information on new photographic base maps.
Obtaining Wetland Maps
WWI maps number 1,800, printed on paper at a size of 24" X 24", each depicting a 36 square mile area at a scale of 1:24,000 (1"=2,000').
For the desired map you need to know the county, township number and the range number. Maps cost $5.00 each and are available from the DNR.
Order forms are available from your local DNR office. Digital maps are also available. Check out the Wisconsin Wetland Inventory GIS Data web page for more information.
For information about the availability of Digital Wisconsin Wetland Inventory, or to order data, contact:
Lois Stoerzer
Wisconsin Wetland Inventory Coordinator
DNR, Bureau of Fisheries Management & Habitat Protection
P.O. Box 7921
Madison, WI 53707-7921
Email: stoerl@mail01.dnr.state.wi.us
(608) 266-8852
Note: The information in this article is based primarily on A User's Guide to the Wisconsin Wetland Inventory, and Wisconsin Wetland Inventory Classification Guide. Both guides are produced by and are available from the WisDNR.
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