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<br />" <br /> <br />the lOa-year floodplain IS divided into a floodway and a floodway <br />fringe. The floodway 15 the channel of a stream, plus any <br />adjacent floodplain areas, that must be kept free of encroachment <br />so that the lOa-year flood can be carried without substantial <br />increases in flood heights. Minimum federal standards 1 imi t such <br />increases to 1.0 foot, provided that hazardous velocities are not <br />produced. The floodways in this study are presented to local <br />agencies as minimum standards that can be adopted directly or that <br />can be used as a basis for additional floodway studies. <br /> <br />The floodways presented in this study were computed on th.. basis <br />of equal conveyance reduction from each side of the floodplain. <br />The results of these computations are tabulated at selected cross <br />sections for each stream segment for which a floodway is computed <br />(Table 2). <br /> <br />As shown on the Flood Boundary and Floodway Map (Exhibit 2), the <br />floodway boundaries were computed at cross sections. Between <br />cross sections, the boundaries were interpolated. In cases where <br />the floodway and lOa-year floodplain boundaries are either close <br />together or collinear, only the floodway boundary has been shown. <br /> <br />The area between the floodway and lOa-year floodplain boundaries <br />is termed the floodway fringe. The floodway fringe encompasses <br />the portion of the floodplain that could be completely obstructed <br />without increasing the water-surface elevation of the IOO-year <br />flood by more than 1.0 foot at any point. Typical relationships <br />between the floodway and the fringe and their significance to <br />floodplain development are shown in figure 2. <br /> <br />I- <br /> <br />100.VEAR l=LOOO PLAIN <br /> <br />-, <br /> <br />Fl.OOOWAV <br />FRINGE <br /> <br /> <br />FLOODWAY <br /> <br />j: LOOOWA Y <br />FRI!'IIGE <br /> <br />STREAM <br />CI-oIAN....EL <br /> <br />FLOOD ELEVATION WMEN <br />CONFINED WITHIN FLOODWAY <br /> <br /> <br />~ <br /> <br /> <br />o <br /> <br />ARE~ OF FlOOD PLAIN THAT COULD <br />BE USED FDA OEVELOPMENT BY <br />RAISING GROUND <br /> <br />fLOOD ELEVATION <br />aEFQAEENCROACHMENT <br />ON FLOOO PLAIN <br /> <br />LINE A8 IS THE FLOOD ELEVATION BEFORE ENCROACHMENT. <br />LINE CO IS THI! FLOOD ELEVATION AFTER ENCROACHMENT. <br />.SURCHARGE IS NOTTO EXCEED 1.0 FOOT (FEMA REQUIREMENT) OR l..ESSER AMOUNT IF SPECIFIED BY STATE. <br /> <br />figure 2. floodway Schematic <br /> <br />15 <br />