Types of Altered Hydric Soils • Artificial (created) • Drained (Protected, ditched) • Historic (filled) • Relict (geologic alteration)
Caveats • Modified soil and hydrology may be due to illegal or legal activities. • By federal or state agency policy, modified areas may be subject to litigation (Section 404 CWA, Swampbuster) or still eligible for programs (USDA’s EWP).
Hydrologic Modification • Hydrologic modification results where saturation and/or inundation (ponding or flooding) has been changed by human or geologic processes. • Both geologic modifications and human modifications of hydrology may change the hydric status of a soil.
Soil Modification • Soil modification result where soils (not hydrology) have been altered either through geologic or human additions or removals. • Both geologic modifications and human modifications of a soil may change the hydric status of a soil.
Development of Altered Soils • Hydrologic modification may result in: 1. Artificial Hydric Soils (created) 2. Drained (Protected, ditched) Hydric Soils. • Soil modification may result in: 1. Artificial Hydric Soils (created) 2. Historic Hydric Soils (filled) 3. Relict Hydric Soils (geologic alteration)
Hydric Soils • …formed under conditions of saturation, flooding, or ponding; and anaerobic conditions. • Soil modifications are typically not needed to maintain or restore a wetland where hydric soils exist. (Exception, relict hydric soils) • For example, drained hydric soils need only removal of hydrologic modifications to restore the wetland.
Nonhydric Soils • Soil and/or hydrology modifications are needed to create a wetland.
How is a Soil Identified as Hydric • A soil is identified as hydric because it: 1. Has a hydric soil indicator, or 2. Meets hydric soil criteria 3 or 4, or 3. By data meets the Hydric Soil Technical Standard (HSTS).
Artificial Hydric Soils(created) • Wetness of these altered soils has been increased by human activities (constructed wetlands, irrigation leaks, rice fields, lake skeins and other construction activities) or the soils have been altered by human activities (constructed wetlands, pond fringes and other excavations). • These altered soils are hydric soils because they: 1. Have a hydric soil indicator, or 2. Meet hydric soil criteria 3 or 4, or 3. By data meet the HSTS.
Artificial Hydric Soil Excavation This dug pond has an artificial hydric soil fringe that was created when the pond was constructed. It now supports a wetland ecosystem.
Artificial Hydric Soil Hydrology Alteration Construction activities, note the railroad in the background, may be the reason wetlands and hydric soils exist here.
Artificial Hydric Soil Created Wetland The wetland shown here and on the first slide was created by removing soil material from a nonhydric soil. The resulting soil is an Artificial Hydric Soil.
Drained (Protected, ditched) Hydric Soils • An attempt through human activities to decrease the wetness of these altered soils has been made (ditches, levees, dams, pumps, etc.). • Even with reduced wetness these altered soils maintain their hydric status because they: 1. Have a hydric soil indicator or, 2. Meet hydric soil criteria 3 or 4 or, 3. By data meet the HSTS.
Ditches, levees, dams, pumps, etc., • do not alter the hydric status of a soil.
Drained Hydric soils • May remain a functional hydric soil. • May no longer experience periods of anaerobic conditions in the upper part and are therefore, not a functional hydric soil. • The HSTS could be used to determine if a drained soil remains a functional hydric soils
Historic (Filled) Hydric Soils • These altered soils have had additional soil material placed on top of the original soil by human activities to the extent that that they are no longer hydric (1992 flooding deposition on the Missouri River flood plain, filling a wetland). The additions may be intentional (illegal fill) or non intentional (erosional deposition). • These altered soils are nonhydric because they: 1. Do not have a hydric soil indicator and, 2. Do not meet hydric soil criteria 3 or 4 and, 3. Do not, by data, meet the HSTS.
Historic Hydric Soils are altered soils that were once hydric but have had human modifications (additions) such that they are no longer hydric. The additions may be intentional (illegal fill) or non intentional (erosional deposition). Nonhydric Hydric 15 cm
Historic Hydric Soils • Even though fill material has been placed over an entire soil area there may be areas that are still hydric as well as areas that are no longer hydric.
Areas which may have changed from hydric to nonhydric. Channelization and the resulting spoil may change the hydric status of a soil. Also the surrounding area may have reduced wetness. Culvert
Relict Hydric Soils • These altered soils were once hydric but are no longer hydric due to geologic activities (pimple mounds of Texas Gulf Coast Prairie, stream downcutting). • Only on close examination is it evident that hydric soil morphologies do not exist. • These altered soils are nonhydric because they: 1. Do not have a hydric soil indicator and, 2. Do not meet hydric soil criteria 3 or 4 and, 3. Do not, by data, meet the HSTS.
Hydric Soils and Mitigation • Enhancement • Restoration • Creation
Enhancement • Restoring disturbed jurisdictional wetlands to their original functional capacity • Soils may be drained or historic, but hydrology was not altered to the point that the soils are no longer functional hydric soils
Historic and drained hydric soils that would qualify for enhancement. Functional historic hydric soil Functional drained hydric soil
Restoration • Restoring disturbed sites that were once jurisdictional wetlands, but are no longer. • Soils may be drained or historic and no longer functional hydric soils. • Restoration is much easier than creation to establish wetland hydrology.
Historic and drained hydric soils that would qualify for restoration. Non-functional historic hydric soil Non-functional drained hydric soil
Restoration to Functional Hydric Soil • Prior converted cropland may not need restoration to establish a functional hydric soil. • Historic hydric soils would require removal of fill material. • Drained hydric soils would require removal of structures or plugging of ditches. • HSTS can be used to evaluate if soils have become functional hydric soils.
Creation • Wetlands are created in an area where wetlands have never existed. • Soils are not hydric soils.
Creation of Artificial Hydric Soils • Hydrology may be altered so soils become anaerobic in the upper part (dams, water control structures, soil compaction). • Soils may be excavated to water table so that they become anaerobic in the upper part. • HSTS and/or close examination of redox feature formation can be used to evaluate if soils have become functional hydric soils. • Caution, if soils are excavated and sufficient organic matter has not been reapplied to surface, redox feature formation will be limited.
Soil Morphology Backfill with organic ammendment Excavate?
Summary • The types of Altered Hydric Soils are Artificial, Drained (Protected), Historic (Filled), and Relict hydric soil. • Artificial hydric soils were once nonhydric but now are hydric soils. • Drained hydric soils were hydric and are still hydric soils but may not be functional. • Historic hydric soils were once hydric but are typically now nonhydric soils.
Summary (cont.) • Relict hydric soils were hydric but are now nonhydric soils: created by geologic modifications to hydrology. • To identify if a disturbed soil is hydric it must either (1) have a hydric soil indicator or, (2) meet hydric soil criteria 3 or 4 or, (3) by data meets the HSTS. • Wetland mitigation can include enhancement (hydric soils), restoration (nonfunctional drained hydric soils, historic hydric soils, or hydric soils on prior converted cropland), or creation (nonhydric soils).
Literature Cited • Hurt, G.W., P.M. Whited, and R.F. Pringle (Eds.). 2002. Field indicators of hydric soils in the United States (Version 5.0), USDA, NRCS, Fort Worth, TX. http://soils.usda.gov/soil_use/hydric/field_ind.pdf • Vepraskas, M. J. 1994. Redoximorphic Features for Identifying Aquic Conditions. Tech. Bulletin 301. North Carolina Ag. Research Service, North Carolina State Univ., Raleigh, North Carolina.