Problem Wetlands and Challenging Field Situations

Authored by: Ralph W. Tiner

Wetland Indicators

Print publication date:  November  2016
Online publication date:  December  2016

Print ISBN: 9781439853696
eBook ISBN: 9781315374710
Adobe ISBN:


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Depending on the criteria established for wetland identification, there may be a few or many exceptions to the “rule,” for every rule has exceptions. Many wetlands have been altered by drainage activities to a degree that necessitates an assessment of their hydrology, while other wetlands are intermixed with nonwetlands that makes wetland delineation challenging. Following the Corps wetland delineation manual, wetlands subject to regulation under the Clean Water Act must typically pass a three-factor test; they must have positive indicators of the three factors (vegetation, soils, and hydrology) that are associated with wetlands, with a few noted exceptions (Environmental Laboratory, 1987). To be designated as a potentially regulated wetland, an area must possess at the time of inspection or be expected to normally have hydrophytic vegetation, hydric soils, and certain signs of wetland hydrology (see Chapter 6 for details). Using this rule, a number of typical wetlands fail the three-factor test and must be considered exceptions. For example, hemlock swamps may not have vegetation that meets the Corps basic rule for hydrophytic vegetation since eastern hemlock (Tsuga canadensis) is a facultative upland (FACU) species. Some wetlands may possess soils that do not exhibit hydric soil properties. Other wetlands may not have signs of wetland hydrology at the time of the inspection or may be subject to drainage where an investigation of water table dynamics may be necessary to see if the area is still wet enough to qualify as wetland. The wetlands mentioned earlier are considered “problem wetlands” or “difficult wetland situations” from a wetland identification and delineation standpoint due to the lack of one or more indicators or significantly altered wetland hydrology. These wetlands are not necessarily less valuable or less wetland than other types, but simply present difficulties for identification when strictly applying a three-factor test.

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