Compensating for Wetland Losses Under the Clean Water Act (2001) / Chapter Skim
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7 Technical Approaches Toward Achieving No Net Loss
7 Technical Approaches Toward Achieving No Net Loss
Pages 123-137
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From page 123... ...
OPERATIONAL GUIDELINES FOR CREATING OR RESTORING WETLANDS THAT ARE ECOLOGICALLY SELF-SUSTAINING The compensatory mitigation process has been weakened by insufficient scientific knowledge as well as limitations of wetland regulatory institutions. The committee agreed on 10 guidelines applicable to compensatory mitigation projects.
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From page 124... ...
As described in other chapters, regulatory agency personnel often do not have either the time or the education and training to consider important, broader issues such as landscape setting. It is imperative that the Corps, EPA, and other advisory agency personnel receive additional training in landscape ecology and other considerations that are poorly represented in the present mitigation process.
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From page 125... ...
Promote naturally variable hydrology, with emphasis on enabling fluctuations in water flow and level, and duration and frequency of change, representative of other comparable wetlands in the same landscape setting. Preferably, natural hydrology should be allowed to become reestablished rather than finessed through active engineering devices to mimic a natural hydroperiod.
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From page 126... ...
Whenever possible, avoid manipulating wetland processes using approaches that require continual maintenance. Avoid hydraulic control structures and other engineered structures that are vulnerable to chronic failure and require maintenance and replacement.
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From page 127... ...
can alter the timing, frequency, amplitude, and duration of inundation. In the case of some less-studied, restored wetland types, there is little scientific or technical information on natural microtopography (e.g., what causes strings and flarks in patterned fens or how hummocks in fens control local nutrient dynamics and species assemblages and subsurface hydrology are poorly known)
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From page 128... ...
WETLAND FUNCTIONAL ASSESSMENT The goal of no net loss refers to both wetland acres and wetland function, as the functions contribute to the watershed where the wetland is located. Therefore, when setting compensatory mitigation goals, the functions of a wetland proposed for fill need to be precisely characterized
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From page 129... ...
Most wetland scientists argue that science-based, regionally standardized procedures are preferable to best professional judgment in comprehensively evaluating wetland function for both impacted and mitigation sites. As a result, the general absence of a uniform approach to assessing wetlands as multifunctional ecosystems have likely encouraged less complex wetland mitigation designs and rudimentary measures of achieving mitigation goals.
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From page 130... ...
In many areas, floristic assessment has been the method of choice because vegetation parameters are easy to measure, provide a dramatic visual indicator of compliance (full canopy, tall trees) , and allow resource agencies to write well-defined performance criteria for the mitigation sites.
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From page 131... ...
It was seen as particularly applicable to wetland mitigation because target hydrology could be based on the influence of water sources, wetland type, and the relative ease or difficulty of establishing certain hydrological regimes. Another of the recognized strengths of HGM is the assessment of functional performance based on a domain of reference systems that capture the presumed optimum natural function.
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From page 132... ...
However, in one respect, HGM and similar assessment procedures are still deficient at assessing the effect of wetland mitigation at the landscape scale. Although they may effectively assess the functions of a wetland site in a hydrogeomorphic, landscape setting, these procedures will not necessarily examine whether the development of a wetland will reduce the functional value of adjacent wetlands or put at risk significant other areas.
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From page 133... ...
However, HGM has many useful applications in functional assessment and the mitigation process in general. For instance, the advantages of evaluating mitigation performance using an assessment of hydrological equivalence (Bedford 1996)
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From page 134... ...
Although HGM as a specific functional assessment procedure may not be meeting expectations and may be too costly to implement in all cases, it has put a focus on the need for assessing wetland function at the landscape scale (see Box 7-2~.
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From page 135... ...
TECHNICAL APPROACHES TOWARD ACHIEVING NO NET LOSS 135 Furthermore, it should be recognized that, as it is currently developed as an assessment tool, HGM is principally a diagnostic method, not a prescriptive "cookbook." In this respect, the HGM models do not specifically lay out design parameters that guarantee the likelihood that hydrology, desired wetland vegetation, and desired animals will be reestab
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From page 136... ...
RECOMMENDATIONS 1. Dependence on subjective, best professional judgment in assessing wetland function should be replaced by science-based, rapid assessment procedures that incorporate at least the following characteristics: · Effectively assess goals of wetland mitigation projects.
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From page 137... ...
2. Impact sites should be evaluated using the same ~ncUonal assessment tools used for the m1Ugat10n she.
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