Hydric Soils - Overview

The Hydric Soils section presents the most current information about hydric soils. It updates information that was previously published in “Hydric Soils of the United States” and coordinates it with information that has been published in the “Federal Register”. It also includes the most recent set of field indicators of hydric soils.

Four types of technical information about hydric soils are presented.

  • The current definition of a hydric soil — This definition has been consistent in the overall concept that hydric soils are those soils that are sufficiently wet in the upper part to develop anaerobic conditions during the growing season.
  • The database selection criteria for hydric soils and the lists which are generated from them — The database selection criteria are selected soil properties that are documented in Soil Taxonomy and were designed primarily to generate a list of potentially hydric soils from soil survey databases. Only criteria 1, 3, and 4 can be used in the field to determine hydric soils; however, proof of anaerobic conditions must also be obtained for criteria 1, 3, and 4 either through data or best professional judgment (from Tech Note 1). The primary purpose of these selection criteria is to generate a list of soil map unit components that are likely to meet the hydric soil definition. Caution must be used when comparing the list of hydric components to soil survey maps. Many of the soils on the list have ranges in water table depths that allow the soil component to range from hydric to nonhydric depending on the location of the soil within the landscape as described in the map unit. Lists of hydric soils along with soil survey maps are good off-site ancillary tools to assist in wetland determinations, but they are not a substitute for observations made during on-site investigations.
  • The list of field indicators of hydric soils — The field indicators are morphological properties known to be associated with soils that meet the definition of a hydric soil. Presence of one or more field indicators suggests that the processes associated with hydric soil formation have taken place on the site being observed. The field indicators are essential for hydric soil identification because once formed, they persist in the soil during both wet and dry seasonal periods.
  • The Hydric Soil Technical Notes — Contain National Technical Committee for Hydric Soils (NTCHS) updates, insights, standards, and clarifications.