Criteria - Technical requirements upon which a judgment or decision may be based. 



Deepwater habitat - Any open water area in which the mean water depth exceeds 6.6 feet at mean low wa- 

 ter in nontidal and freshwater tidal areas, or is below extreme low water at spring tides in salt and brackish 

 tidal areas, or the maximum depth of emerging vegetation, whichever is greater. 



Density - The number of individuals per unit area. 



Detritus - Fragments of plant parts found on the soil surface or in water; when fused together by algae or 

 soil particles, this detritus is an indicator that the soil surface was recently inundated. 



Diameter at breast height (dbh) - The width of a plant stem (e.g., tree trunk) as measured at 4.5 feet above 

 the ground surface. 



Dike - An embankment (usually of earth) constructed to keep water in or out of a given area. 



Disturbed area - An area where vegetation, soil, and/or hydrology have been significantly alteied, thereby 

 making a wedand determination difficult. 



Dominance - As used herein, refers to the spatial extent of a species; commonly the most abundant species 

 in each vegetation stratum that, when ranked in descending order of abundance and cumulatively totaled, 

 immediately exceeds 50 percent of the total dominance measure (e.g., areal cover or basal area) for the 

 stratum, plus any additional species comprising 20 percent or more of the total dominance measure for the 

 stramm. 



Dominance measure - The means or method by which dominance is established, including areal coverage 

 and basal area; the total dominance measure is the sum total of the dominance measure values for all spe- 

 cies comprising a given stratum. 



Dominance threshold number - The number at which 50 percent of the total dominance measure for a given 

 stratum is represented by one or more plant species when ranked in descending order of abundance (i.e., 

 from most to least abundant); when this number is immediately exceeded, the dominant species for the 

 stratum are realized. 



Dominant species - For each stratum, dominant species are those that, when ranked in descending rank or- 

 der and cumulatively totaled, immediately exceed 50 percent of the total dominance measure (i.e., the dom- 

 inance threshold number), plus any additional species comprising 20 percent or more of the total domi- 

 nance measure for the stratum. 



Drained, effectively - A condition where ground or surface water has been removed by artificial means to 

 the point that an area no longer meets the wetland hydrology criterion. 



Drift line - An accumulation of water-carried debris along a contour or at the base of vegetation that pro- 

 vides direct evidence of prior inundation and often indicates the directional flow of flood waters. 



Duff - The matted, partly decomposed, organic surface layer of forested soils. 



Duration (of inundation or soil saturation) - The length of time that water stands above the soil surface (in- 

 undation), or that water fills most soil pores near the soil surface; as used herein, "duration" refers to a per- 

 iod during the growing season. 



Entisols - Soils of slight or recent development; common along rivers and floodplains. 



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