Primary purpose
To evaluate wetlands in planning, education, and wetland inventory; but, not for detailed impact analysis on individual wetlands.
Expertise needed
Public officials and others familiar with wetlands, but who are not necessarily wetland specialists. These individuals must have received training in OFWAM.
Applicable habitat types
Freshwater wetlands in Oregon.
Categories assessed
Nine functions are addressed: wildlife habitat; fish habitat; water quality; hydrologic control; sensitivity to impact; enhancement potential; education; recreation; and aesthetic quality.
Procedure
The user reviews existing data sources and visits the area to answer questions in the "wetland characterization" and "wetlands of special interest for protection" data sheets. Then, this information is used to complete data sheets for each function that (a) contain assessment questions, (b) list three conditions for each question, and (c) provide criteria for selecting an environmental descriptor. Finally, previously answered questions are used to complete the "watershed summary sheet" to describe how the wetland interacts with the landscape.
Key Terminology
Condition: the integrity of a wetland’s physical and biological structure. This determines the wetland’s ability to perform specific functions, as well as its resilience and enhancement opportunities.
Evaluation descriptor: summary statement describing whether the wetland (1) is intact, (2) impacted or degraded, or (3) function is lost or not present.
Function: characteristic action or behavior associated with a wetland that contributes to a larger
ecological condition such as wildlife habitat, fish habitat, water quality, and/or flood control.
Output
Indication of whether wetland function is intact, degraded, or not present.
Estimated time to assess 1 acre site
Total 10-26 hours.
8-24 hours: Select assessment area (step 1), assemble available information (step 2), determine watershed boundary (step 3), and prepare wetland base maps and overlays (step 4).
1 hour per wetland: Complete Wetland Characterization and Wetlands of Special Interest section (step 5) and answer function/condition assessment questions and apply criteria (step 6).
1 hour per wetland: Complete function and condition summary sheet (step 7) and watershed summary sheet (step 8).
Comparison of habitat types
Can directly compare freshwater wetlands within a planning area.
Use as guide to design
OFWAM should not be used as a guide to design; however, individual variables (assessment questions) may provide useful information. It is not the intended purpose for the procedure; therefore, it contains properties that limit its application for this purpose. For example, OFWAM uses opportunity variables, but does not set upper limits on those opportunities that could potentially reduce function (e.g., a severe water quality condition entering the wetland from the watershed is considered a preferred condition for the water quality function). In some circumstances, a wetland may not have the capacity to remove all nutrient input. An upper limit on the opportunity must be defined to insure that the existing or planned wetland can predictably have the capacity to provide a function. Also, OFWAM does not provide validated threshold values for many variables. Some of the variables may provide useful information.
Contact Person
Dana Field, Wetlands Program, Oregon Division of State Lands, 775 Summer St. NE, Salem, OR 97310 phone: (503) 378-3805 ext. 238; fax: (503) 378-4844; e-mail: dana.field@dsl.state.or.us
Related procedures
The NH Method (Ammann et al. 1991) was a template for OFWAM; however, there are substantial differences. In addition to adapting the models to Oregon, OFWAM differs in the following ways:
• Several functions have been removed or combined.
• The scoring and output differs. The NH Method assigns a functional value index (scale 0-1.0) to each question, whereas OFWAM does not. The indices in the NH Method are used to calculate the "average functional value index", whereas, OFWAM uses responses to questions to derive an "evaluation descriptor" for each function.
• OFWAM does not provide a measure of function that incorporates acreage.
Extent of use/field testing
OFWAM was field tested during initial development and revised for the second edition (published April 1996). OFWAM has been applied in at least 22 comprehensive city-wide wetland inventories to date, with the results used as a basis for local wetland conservation ordinances. It has also been used as a rough guide for assessing impacts to individual wetlands for mitigation of lost functions.
Proposed future revisions
None.
Key Reference
Roth, E., R. Olsen, P. Snow, and R. Sumner. 1996. Oregon Freshwater Wetland Assessment Methodology. 2nd edition. Oregon Division of State Lands, Salem, OR.