1987 Wetland Delineation Manual - The Wetlands Regulation Center

Wetland Delination Manual, 1987 78
Basal area - The cross-sectional area of a tree trunk measured in square inches, square
centimetres, etc. Basal area is normally measured at 4.5 ft above the ground level and is used
as a measure of dominance. The most easily used tool for measuring basal area is a tape
marked in square inches. When plotless methods are used, an angle gauge or prism will
provide a means for rapidly determining basal area. This term is also applicable to the
crosssectional area of a clumped herbaceous plant, measured at 1.0 in. above the soil surface.
Bench mark - A fixed, more or less permanent reference point or object, the elevation of which
is known. The US Geological Survey (USGS) installs brass caps in bridge abutments or
otherwise permanently sets bench marks at convenient locations nationwide. The elevations
on these marks are referenced to the National Geodetic Vertical Datum (NGVD), also
commonly known as mean sea level (MSL). Locations of these bench marks on USGS
quadrangle maps are shown as small triangles. However, the marks are sometimes destroyed
by construction or vandalism. The existence of any bench mark should be field verified before
planning work that relies on a particular reference point. The USGS and/or local state
surveyor's office can provide information on the existence, exact location, and exact elevation
of bench marks.
Biennial - An event that occurs at 2-year intervals.
Buried soil - A once-exposed soil now covered by an alluvial, loessal, or other deposit
(including man-made).
Canopy layer - The uppermost layer of vegetation in a plant community. In forested areas,
mature trees comprise the canopy layer, while the tallest herbaceous species constitute the
canopy layer in a marsh.
Capillary fringe - A zone immediately above the water table (zero gauge pressure) in which
water is drawn upward from the water table by capillary action.
Chemical reduction - Any process by which one compound or ion acts as an electron donor.
In such cases, the valence state of the electron donor is decreased.
Chroma - The relative purity or saturation of a color; intensity of distinctive hue as related to
grayness; one of the three variables of color.
Comprehensive wetland determination - A type of wetland determination that is based on the
strongest possible evidence, requiring the collection of quantitative data.
Concretion - A local concentration of chemical compounds (e.g. calcium carbonate, iron
oxide) in the form of a grain or nodule of varving size, shape, hardness, and color.
Concretions of significance in hydric soils are usually iron and/or manganese oxides occurring
at or near the soil surface, which develop under conditions of prolonged soil saturation.
25 February 1997 Environmental Techncal Services Co. 834 Castle Ridge Rd Austin, Texas 78746