Laserfiche WebLink
Custom Soil Resource Report <br />Flooding is the temporary inundation of an area caused by overflowing streams, by <br />runoff from adjacent slopes, or by tides. Water standing for short periods after rainfall <br />or snowmelt is not considered flooding, and water standing in swamps and marshes <br />is considered ponding rather than flooding. <br />Duration and frequency are estimated. Duration is expressed as extremely brief if 0.1 <br />hour to 4 hours, very brief if 4 hours to 2 days, brief if 2 to 7 days, long if 7 to 30 days, <br />and very long if more than 30 days. Frequency is expressed as none, very rare, rare, <br />occasional, frequent, and very frequent. None means that flooding is not probable; <br />very rare that it is very unlikely but possible under extremely unusual weather <br />conditions (the chance of flooding is less than 1 percent in any year); rare that it is <br />unlikely but possible under unusual weather conditions (the chance of flooding is 1 to <br />5 percent in any year); occasional that it occurs infrequently under normal weather <br />conditions (the chance of flooding is 5 to 50 percent in any year); frequent that it is <br />likely to occur often under normal weather conditions (the chance of flooding is more <br />than 50 percent in any year but is less than 50 percent in all months in any year); and <br />very frequent that it is likely to occur very often under normal weather conditions (the <br />chance of flooding is more than 50 percent in all months of any year). <br />The information is based on evidence in the soil profile, namely thin strata of gravel, <br />sand, silt, or clay deposited by floodwater; irregular decrease in organic matter content <br />with increasing depth; and little or no horizon development. <br />Also considered are local information about the extent and levels of flooding and the <br />relation of each soil on the landscape to historic floods. Information on the extent of <br />flooding based on soil data is less specific than that provided by detailed engineering <br />surveys that delineate flood-prone areas at specific flood frequency levels. <br />30