APPENDIX C. Hydric Soils 



Definition (USDA, SCS 1985a): A hydric soil is a soil that in its undrained condition is saturated, flooded, or 

 ponded long enough during the growing season to develop anaerobic conditions that favor the growth 

 and regeneration or hydropnytic vegetation. 



Criteria for hydric soils (soil orders, groups, and types are defined in USDA, SCS 1985a): 



1. All Histosols except Folists, or 



2. Soils in Aquic suborders, Aquic subgroups, Albolls suborder, Salorthids great group, or Pell great 

 groups of Vertisols that are: 



a. somewhat poorly drained and have water table less than 0.5 ft from the surface at some 

 time during the growing season, or 



b. poorly drained or very poorly drained and have either: 



I. water table at less than 1 .0 ft from the surface at some time during the growing 



season if permeability is equal to or greater than 6.0 inches/hr in all layers 

 within 20 inches, or 



ii. water table at less than 1 .5 ft from the surface at some time during the growing 



season if permeability is less than 6.0 inches/hr in any layer within 20 inches, 

 or 



3. Soils that are ponded during any part of the growing season, or 



4. Soils that are frequently flooded for long duration during the growing season. 



pH modifiers (from Cowardin et al. 1979): 



Modifier pH of Water 



Acid <5.5 



Circumneutral 5.5-7.4 



Alkaline 7.4 



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