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I <br /> U.S. DEPARTMENT OF AGRICULTURE PAGE 2 OF 3 <br /> TURAL RESOURCES CONSERVATION SERVICE 01/28/97 <br /> ' WATER FEATURES <br /> note -- WATER FEATURES <br /> This report gives estimates of various soil water features. The estimates are used in land use planning that involves <br /> ineering considerations. <br /> rologic soil groups are used to estimate runoff from precipitation. Soils not protected by vegetation are <br /> assigned to one of four groups. They are grouped according to the infiltration of water when the soils are thoroughly <br /> and receive precipitation from Long-duration storms. The four hydrologic soil groups are: <br /> Group " A". Soils having a high infiltration rate (low <br /> ' runoff potential) when thoroughly wet. These consist mainly <br /> of deep, well drained to excessively drained sands or <br /> gravelly sands. These soils have a high rate of water <br /> ' transmission. <br /> Group "B". Soils having a moderate infiltration rate when <br /> thoroughly wet. These consist chiefly of moderately deep or <br /> deep, moderately well drained or well drained soils that <br /> have moderately fine texture to moderately coarse texture. <br /> These soils have a moderate rate of water transmission. <br /> ' Group "C". Soils having a stow infiltration rate when <br /> thoroughly wet. These consist chiefly of soils having a <br /> Layer that impedes the downward movement of water or soils <br /> ' of moderately fine texture or fine texture. These soils <br /> have a slow rate of water transmission. <br /> ' Group "D". Soils having a very slow infiltration rate (high <br /> runoff potential) when thoroughly wet. These consist <br /> chiefly of clays that have a high shrink-swell potential, <br /> ' soils that have a permanent high water table, soils that <br /> have a claypan or clay layer at or near the surface, and <br /> soils that are shallow over nearly impervious material. <br /> These soils have a very slow rate of water transmission. <br /> �a soil is assigned to two hydrologic groups in this report, the first letter is for drained areas and the second <br /> is for undrained areas. Flooding, the temporary inundation of an area, is caused by overflowing streams, by runoff from <br /> acent slopes, or by tides. Water standing for short periods after rainfall or snowmelt is not considered <br /> oding, nor is water in swamps and marshes. This report gives the frequency and duration of flooding and <br /> the time of year when flooding is most likely. Frequency, duration, and probable dates of occurrence are estimated. <br /> iquency is expressed as "None", "Rare", "Occasional", and "Frequent". "None" means that flooding is not probable; <br /> re" that it is unlikely but possible under unusual weather conditions; "Occasional" that it occurs, on the <br /> average, once or less in 2 years; and "Frequent" that it occurs, on the average, more than once in 2 years. <br /> L,ation is expressed as "Very brief" if less than 2 days, "Brief" if 2 to 7 days, "Long" if 7 to 30 days, and "Very <br /> tong" if more than 30 days. The information is based on evidence in the soil profile, namely thin strata of gravel, <br /> Id, silt, or clay deposited by floodwater; irregular decrease in organic matter content with increasing depth; <br /> absence of distinctive horizons that form in soils that are not subject to flooding. Also considered are local <br /> n ormation about the extent and levels of flooding and the relation of each soil on the landscape to historic floods. <br /> 1 <br />