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ADDENDUM 9-6-2 (Cont.) <br />Soil Interpretations <br />FOOTNOTES <br />10 1 Factor: This value Indicates the relative amount of soil that can be expected to erode, through wind influence, in Tons-Per-Acre-Per-Year (T/AC/YR). It <br />is related to the Nind erodibility Group number and the percent of dry soil aggregates greater than 0.84 mm in diameter. Values are taken from USDA-SCS <br />(May 1981), Myoming Soil Procedures Guide, p. 35. <br />11 K Factor: This value indicates the re lot lve susceptibility of a surface soil to water erosion. Values may range from .00 to .70. Higher K values <br />indicate higher erosion susceptibility. Sofls with K factor over about 0.40 are generally considered to be highly susceptible to water erosion. It should <br />be noted that the K factor is primarily derived from physical characteristics of the soil, and does not reflect other soil erosion factors such as <br />management practices, precipitation, or length and steepness of slope. <br />Low Ervdibil7ty: .20 or less; Moderate Erod ibility: .21 - .40; High Erodibi ltty: greater than .40 <br />12 Hydrologic Group Classification of Soils: Hydrologic soil groups are used in watershed planning to estimate runoff from rainfall. Sail properties are <br />considered that influence the minimum rate of tnfil tra tton obtained for a bare so11 after prolonged wetting. These properties are: depth of seasonally <br />high water table, intake rate and permeabilf ty after prolonged wetting, and depth to a very slowly permeable layer. The influence of ground cover is <br />~O treated independently - not in hydrologic soil groupings. <br />rn <br />i <br />~ The soils have been classified into four groups, A through D. The individual class if ica dons are estimated from USDA-SLS (May 1981), Myoming Soil <br />Procedures Guide, p. 42-44 and compared with the mast current official USDA-SCS soil series "Form 5" sheets. Statements in parentheses following the <br />definitions may be helpful to soil scientists wishing to place soils Into hydrologic groups using the sail classifiea tton system. <br />A. (Low runoff potential). Soils have high (ra pld) infiltration rates even when thoroughly wetted and consist chiefly of deep, well to excess tvely <br />drained sands or gravels. These soils have a high rate of water transmission. (Includes Psamments .except those in Lithic, Aqu ic, and Aquodic <br />subgroups; soils in Grossaren is Subgroups of Undults and Udalfs, and soils in Arenic subgroups of Udults and Udalfs except those in clayey or fine <br />families). <br />,o B. (Moderately low runoff potential). Soils have moderate 1nf11tra ti on rates when thoroughly wetted and consist chiefly of moderately deep to deep, <br />moderately well to well drained soils with moderately fine to moderately coarse textures with moderately slow to moderately rapid permeability. These <br />soils have a moderate rate of water transmission. (Soils other than those in groups A, L, or D). <br />i <br />0 <br />rn <br />m <br />• • • <br />