Wetlands Characteristics and Boundaries (1995) / Chapter Skim
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10 FUNCTIONAL ASSESSMENT OF WETLANDS
10 FUNCTIONAL ASSESSMENT OF WETLANDS
Pages 215-226
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From page 215... ...
Many wetland functions are considered useful or important by society. For example, inundation of wetlands can prevent flood damage elsewhere, denitrification can improve water quality, wetland habitat can help maintain waterfowl populations, and anaerobiosis can influence the development of unique plant communities that contribute to the conservation of biodiversity.
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From page 216... ...
GENERAL REQUIREMENTS FOR FUNCTIONAL ASSESSMENT Important concepts in functional assessment of wetlands include functional capacity, predictors of function (indicators) , and thresholds for functions.
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From page 217... ...
Functional assessment allows comparison of a wetland to other wetlands or to other potential uses of a wetland site, and it shows the extent of compensatory mitigation that might be necessary if a wetland were altered. The first attempt at evaluating wetland functions for regulatory purposes emerged in the USACE permit regulations of 1975, which were revised in 1977 and 1986.
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From page 218... ...
and Adamus (19831. The Method for Wetland Functional Assessment or the FHWA method, as it became known uses an extensive literature review, including evaluation of a large volume of quantitative data, to build a series of evaluation algorithms that represent the functions of wetlands.
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From page 219... ...
, which use observable indexes of conditions and functions to derive rankings and can be used by nonspecialists; the Wisconsin method (Reed, 1986) , which is a modification of the FHWA method; the New Jersey Department of Transportation modification of the FHWA method (McColligan, 1986~; the Virginia Institute of Marine Science method for nontidal wetlands (Bradshaw,1992~; and the Evaluation of Planned Wetlands method (Bartoldus et al., 1994)
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From page 220... ...
In general, methods for wetland evaluation do not provide a means for direct comparison of wetlands on an areal basis, do not provide a basis for estimating mitigation ratios on an areal basis, are not readily adaptable to a variety of wetland types, and have data requirements that are too cumbersome for routine field application. FUTURE METHODS OF FUNCTIONAL ASSESSMENT Assessment Based on Hydrogeomorphic Classification and Reference Wetlands A new procedure for assessment of wetland functions is being developed at the USACE Waterways Experiment Station (WES)
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From page 221... ...
The functional indexes represent only a qualitative approximation of the functional capacity of wetlands. The hydrogeomorphic approach recognizes the reciprocal interactions of wetland ecosystems with the landscape.
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From page 222... ...
This procedure is modeled after the hydrogeomorphic classification system, and was it promulgated in anticipation of the adoption of a wetland evaluation procedure derived from this system by the federal regulatory agencies. Relevance of Hydrologic Factors to Functional Assessment The degree, frequency, and seasonality of inundation vary widely among wetland types (Chapters 2 and 7~.
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From page 223... ...
The degree to which a wetland performs a specific function of value to society does not influence regulatory jurisdiction. Conversely, many activities that can decrease the functional capacity of a jurisdictional wetland are not regulated.
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From page 224... ...
According to the letter, SAMPs, which are labor intensive, can be justified only when an area is environmentally sensitive and under strong pressure for development, the plan is sponsored by a local agency, the public is fully involved, and all parties are willing to conclude the process with regulatory products. Ideal regulatory products include local or state approvals and a USACE general permit for specific activities and local, state, or EPA restrictions for undesirable activities (USACE,1986~.
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From page 225... ...
The environmental community will expect programs that provide flexibility in the management of lower quality wetlands to also provide stringent protection for areas determined to be of high quality. In addition to the flexibility provided in current policy to scale regulatory responses to the effects of specific projects and the functional capacity of specific wetlands, the regulatory program includes provisions for landscape-level planning processes that evaluate the relative value of wetlands.
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From page 226... ...
RECOMMENDATIONS 1. Analysis of wetland functions should be extended and refined, with emphasis on interactions between wetlands and their surroundings and on various hydrogeomorphic classes of wetlands in specific regions.
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