The degree to which a wetland serves any
of these functions depends on its type,
size, landscape position and the level of
disturbance. Although a wetland may
not serve all functions, each wetland
works in combination with other
wetlands or streams as part of a complex
and integrated system. Because of the
importance of these functions, federal
regulations require permittees to avoid,
minimize and mitigate adverse impacts to
Section 404 of the Federal Clean Water
Act of 1972 authorizes the U.S. Army
Corps of Engineers to regulate the
discharge of dredged or fill material into
“waters of the United States,” including
navigable waters, their tributaries and
most wetlands. The following construction
activities, among others, are candidates for
wetland permit consideration:
1. Filling: Placing dredged or fill
materials into a wetland.
2. Excavating: Removing material from
3. Grading: Conducting earthwork to
change the grade or contours of the
4. Clearing: Removing vegetation
(shrubs and trees) from wetlands
by bulldozing or grubbing, and
removing the root structure.
5. Other activities: Such as placing
structures within a wetland and
temporary wetland impacts.
States generally work in conjunction with
federal agencies to coordinate permitting
activities in each state. Examples of such
state agencies include the Wisconsin
Department of Natural Resources
(WDNR), the Ohio Environmental
Protection Agency (OEPA) and the
Michigan Department of Environmental
Quality (Michigan DEQ).
There are online tools available for public
use that map potential wetland areas.
These are based on aerial imagery studies
of topography, drainage patterns and vegetation combined with agency fieldwork
and soil studies. As wetland reports are submitted for respective agency review,
those wetland boundaries can be incorporated in mapping database updates.
Appraisers must use caution when relying on these types of mapping tools to
evaluate the extent of wetlands on a property. First, these are largely based on aerial
imagery and analysis that is subject to seasonal fluctuation in water levels and
vegetation. Second, there may be multiple mapping tools available for the same site,
and each map may show different potential wetland areas. Additionally, wetland
areas may even be shown in different sizes and shapes in each tool. Mapping tools
often include a disclaimer that must be accepted in order to view the map, which
indicates the map is only a guide to potential wetland areas. The following example
shows how the same site in Wisconsin is shown in two different government-provided mapping tools.
The image below shows a recent development site as displayed in the WDNR
online wetland mapping tool. Note that there is an approximate 0.6-acre wetland
area mapped in the northeast quadrant of the site. The same site is shown on page
21using the U.S. Fish and Wildlife Service online mapping tool. Note that there is
no wetland area mapped in the northeast quadrant.
This example demonstrates that it is important to check both the national mapping
tool and the respective state tool if it’s available. In some cases, there may also be
a county or regional planning commission base map as well. In this example, the
Wisconsin mapping tool showed an area with likely wetland characteristics that has
a significant impact to the area of developable land. States agencies like the WDNR
are generally the “front lines” of wetland permitting activities and may have more-updated data based on recent permit applications and more recent field work.
Source: WDNR Surface Water Data Viewer