Download Wetland Delineation

Wetland Delineation
Major Areas Evaluated to
Determine Presence of Wetland

Soils – evidence of past presence of water

Plants – wetland obligate or facultative

Hydrology – sufficient to cause wetland plant and soil
characteristics
Note: for ACOE definition  all three are needed
for EPA any one of three
IMHO – two out of three probably a good compromise
Wetland soils
 soils
that are “…saturated, flooded, or
ponded long enough during the growing
season to develop anaerobic conditions
that favor the growth and regeneration of
hydrophytic vegetation..” (Corps of
Engineers Wetlands Delineation Manual,
1987)
Wetland Soils
 Usually
high in organics
 Show evidence of eluviation

called alluvial soils, usually found in B horizon
 nutrients leached out by water so only clay
is left.
 Generally
soils are the best indicators of
wetlands because alluvial soils will still be
there even after most disturbances
Evaluating the soil for wetland characteristics

Mottled soils have a matrix of one color
with blotches and flecks of other colors
 Gleyed soils are usually light grey with a
bluish or greenish tint (chroma of 1 or less).
Wetland Hydrology
 “The
area is inundated either permanently
or periodically at mean water depths <6.6
ft [2 m], or the soil is saturated to the
surface at some time during the growing
season of the prevalent vegetation.”
(Corps of Engineers Wetlands Delineation
Manual 1987)
Evidence for wetland hydrology on cypress tree trunks
Wetland Plants

“Areas that are inundated or saturated by
surface or ground water at a frequency and
duration sufficient to support, and that under
normal circumstances do support, a prevalence
of vegetation typically adapted for life in
saturated soil conditions” Corps of Engineers
Wetlands Delineation Manual, 1987

hydrophytic vegetation - capable of growing,
competing, and reproducing in saturated soils
which produce, contain, or maintain anaerobic
conditions.
Wetland Plants
 Have
to be able to tolerate anoxia because
roots are covered with water
 Types of wetland plants



Obligate – found in wetlands 100% of the time,
require inundation. If find any  wetland!
Facultative wetland – found in wetlands 66 to
99%  preponderance  wetland!
Mixture of facultative wetland/facultative/upland
– need to take a closer look
Evaluating for wetlands plants
Wetland Plants
Areas Likely to Contain Wetlands

Area occurs in a floodplain or otherwise has low spots in which
water stands at or above the soil surface during the growing season.
Caution: Most wetlands lack both standing water and waterlogged
soils during at least part of the growing season.

Area has plant communities that commonly occur in areas having
standing water for part of the growing season (eg. Cypress-gum
swamps, cordgrass marshes, cattail marshes, bulrush and tule
marshes, and sphagnum bogs).

Area has soils that are called peats or mucks.

Area is periodically flooded by tides, even if only by strong, winddriven, or spring tides.
Used in draft supplement of
1987 delineation manual
Wetland Mitigation

Replace destroyed wetland with artificially
constructed one
 Often fail  use mitigation ratio




Open water
Grasses, wildflowers
Scrub/Shrub
Forested land
1.5:1
2:1
3:1
3-4:1
Note: under certain circumstances the mitigation ratio could be
as high as 10:1.