Value assessment of Jackson-Frazier Wetland, Benton County, Oregon : a case study

Abstract

A growing realization that wetlands are potentially valuable resources has recently stimulated efforts towards their protection. While a foundation for wetland management exists, decision makers still lack adequate tools for addressing issues of wetland preservation vs. development. Wetland preservation values are often neglected in traditional market analyses and in the decision making process. This research uses a wetlands assessment methodology that addresses non-market wetland values in the Willamette Valley, Oregon. The Jackson-Frazier Wetland, north of the Corvallis city limits, is used as a case study for assessment. The Larson Model, a tested assessment model for eastern Massachusetts wetlands, is applied to the Jackson-Frazier Wetland. The model is modified to increase its reproducibility in wetlands classification, accommodate regional differences in the study area, and account for recent information on wetland classification and value assessment. The Jackson-Frazier Wetland qualifies as a high priority site for further assessment under four of eleven criteria: 1. rare plants, 2. visually prominent plants, 3. availability of information, and 4. rare habitat types. The wetland received an adjusted wildlife habitat score of 89 percent (good to excellent) and an adjusted visual-cultural score of 66 percent (moderately good). The wildlife habitat score reflects a complex habitat mosaic spread over a sizable area supporting a diverse and relatively abundant fauna. The visual-cultural score reflects a visually complex landscape dominated by vegetation. The diversity of wetland types, the complex interspersion of wetland classes and subclasses, and the proximity of the wetland to educational institutions combine to offer a variety of visual, educational, and passive recreational opportunities. However, the lack of navigable water bodies, the lack of nearby visually prominent landforms, urban noise, and urban encroachment limit the number and quality of visual-cultural opportunities. The wetland was assessed for its downstream flood mitigation capability under two models with two respective adjusted flood mitigation scores of 967 and 69%. The second score is judged to be more consistent with findings of the Corvallis Drainage Master Plan suggesting the Jackson- Frazier site mitigates floods associated with "common" storm events (e.g., 12% return frequency). Neither flood assessment addresses flooding from the Willamette River during a 100 yearflood. In a separate economic analysis, publicly acquired nonwetland wildlife habitat and visual-cultural areas are used as gauge sites to provide a minimum monetary estimate of preservation values of the Jackson-Frazier Wetland. The derived figure of $ 2,022/acre is compared with several appraised market values of the wetland using preservation value/alternative use value ratios. Ratios greater than one indicate preservation values are greater than alternative use values. Borderline ratios are weighted towards preservation values due to the non-wetland character of the gauge sites. The greatest utility of the applied model is to display traditionally intangible wetland preservation values. This display of values should be considered by resource managers and decision makers in conjunction with a variety of other decision making tools. The validity of a given assessment is directly related to the assumptions and subsequent criteria used. Perceptions of validity are highly influenced by the degree of societal acceptance and use.