Hydric Soil Identification Techniques - Wetland Techniques - page 255

4.11 Soil Surveys and Hydric Soil Lists
Soil surveys are available for most areas and can provide useful information
regarding soil properties and soil moisture conditions. A list of available soil
surveys is located at http://soils.usda.gov/survey/online_surveys/ . Soil maps and
data are available online at http://websoilsurvey.nrcs.usda.gov/ . Soil survey maps
divide the landscape into areas called map units. Map units usually contain more
than one soil type or component. They often contain several minor components or
inclusions of soils with properties that may be similar to or quite different from the
major component. Those soils that are hydric are noted in the Hydric Soils List.
Hydric Soils Lists are developed for each detailed soil survey based on criteria to
identify soil map unit components that are at least in part hydric (Federal Register
[FR Doc. 2012-4733], 2012). These lists rate each soil component as either hydric
or non-hydric based on soil property data. If the soil is rated as hydric, information
is provided regarding whether the soil meets the definition due to saturation,
flooding, or ponding; and on what landform the soil typically occurs. Hydric
Soils Lists are useful to identify areas likely to contain hydric soils. However, not
all areas within a mapping unit or polygon identified as having hydric soils may be
hydric. Conversely, inclusions of hydric soils may be found within soil mapping
units where no hydric soils have been identified.
Soil survey information can be valuable during preliminary data gathering and
synthesis. Landscape relationships and other information that can help identify the
location of the component of the map unit that is hydric vs. non-hydric is also
helpful. Local Hydric Soils Lists are available from state or county NRCS offices
and over the internet from the Field Office Technical Guide, Section 2 ( http://www.
nrcs.usda.gov/technical/efotg/index.html ) or Soil Data Mart ( http://soildatamart.
nrcs.usda.gov/ ) . Local Hydric Soils Lists have been compiled into a National
Hydric Soils List and are available at: http://soils.usda.gov/use/hydric/ .
4.12 Soils That Lack Hydric Soil Indicators
4.12.1 Overview
As stated earlier, the requirements of a hydric soil are those presented in the
definition. Field Indicators were created to assist in identifying those soils that
meet the definition. However, the Field Indicators do not replace or relieve any of
those requirements. If it meets a Field Indicator, it has morphology that indicates
that the soil meets the hydric soils definition and therefore is a hydric soil. However,
if it does not meet a Field Indicator, it may still be a hydric soil if it meets the
requirements in the defintion. Hydric Soils Lists and the Hydric Soil Technical
Standard are two approaches that may lead to an assessment of a soil as hydric by
definition even though it does not meet a Field Indicator.