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6 <br />elevation. The CRITICAL DURATION FLOOD EVENT is generally either the 100-year, <br />24 hour rainfall event as found in NOAA Atlas 14 or the ten-day snow melt event <br />assumed to be 7.2 inches of runoff occurring on frozen ground (CN=100); however, <br />other durations (e.g., 6-hour) may result in the maximum 100-year return period water <br />surface elevation. <br /> DETENTION BASIN. Any natural or man-made depression that stores stormwater <br />runoff temporarily. <br /> DEVELOPMENT. Any land-disturbing activity resulting in creation or reconstruction <br />of impervious surface including, but not limited to, municipal road construction. Normal <br />farming practices part of an ongoing farming operation shall not be considered a <br />DEVELOPMENT. <br /> DRAINAGE SYSTEM. A system of open channel, pipe or tile, to drain property, <br />including laterals, improvements, and improvements of outlets, which may or may not <br />be a public system under the jurisdiction of a watershed district under M.S. Chs. 103B, <br />103D, or 103E. <br /> EMERGENCY OVERFLOW (EOF). A primary overflow to pass flows above the <br />design capacity around the principal outlet safely downstream without causing flooding. <br /> EROSION AND SEDIMENT CONTROL PLAN. A plan of BMPs or equivalent <br />measures designed to control runoff and erosion and to retain or control sediment on <br />land during the period of land disturbance in accordance with the standards set forth in <br />this chapter. <br /> EROSION PREVENTION. Measures employed to prevent erosion including, but not <br />limited to, soil stabilization practices, limited grading, mulch, temporary or permanent <br />cover, and construction phasing. <br /> EXCAVATION. The displacement or removal of soil, sediment or other material. <br /> FILTRATION. A stormwater quality BMP that uses either natural media such as soil <br />or vegetation or manufactured media to trap pollutants such as nutrients and particles in <br />surface water. <br /> FINAL STABILIZATION. All soil disturbing activities at the site have been completed <br />and all soils have to be stabilized by a uniform perennial vegetative cover with a density <br />of 70% over the entire pervious surface area, or other equivalent means necessary to <br />prevent soil failure under erosive conditions. <br /> FLOODPLAIN. The beds proper and areas adjoining a waterbody wetland, lake or <br />watercourse that are inundatedwhich have been or hereafter may be covered by the <br />during the 100-yearregional flood. <br /> FLOODWAY FRINGE. That portion of the floodplain outside of the floodway. Flood <br />fringe is synonymous with the term FLOODWAY FRINGE used in the Flood Insurance <br />study for Anoka County,The area between the floodway and the boundary of the 100- <br />year flood. <br /> FLOODWAY. The channel of a watercourse, the bed of water basins and those <br />portions of adjoining floodplains that must be kept free of encroachment to