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The 100- and SOO-year floodplain boundaries are sbown on tbe Flood Insurance Rate Map (Exhibit 2). On this map, the lOO-year floodplain boundary corresponds to the boundary of the areas of special flood bazards (Zones A, AE, and AO); and the SOG-year floodplain boundary corresponds to the boundary of areas cf moderate flood hazards. In cases where the 100- and SOD-year floodplain boundaries are close together, only the 100-year floodplain boundar7 bas been shown. Small areas within the- floodplain boundaries may lie sbove the flood elevations but cannot be shown due to limitations of the map scale and/or lack of detailed topographic data. For the streams studied flOOdplain boundary is (Exhibit 2). by approximate methods, only the 100-year shown on the Flood Insurance Rate Map 4.2 Floodways Encroachment on floodplains, such as structures and fill, reduces flood-carrying capacity, increases flood heights and velocities. snd increases flood hazards in areas beyond the encroachment itself. One aspect of floodplain management involves balancing the economic gain from floodplain development against the resulting increase in flood hazard. For purposes of the NFIP, a floodway is used as a tool to assist local communities in this aspect of flOOdplain management. Under thi s concept, the area of the 100- year floodplain is divided into a floodway and a floadway fringe. Ihe floodway is the channel of a stream, plus any adjacent floodplain areas, that must be kept free of encroachment so that the lOO-year flood can be carried without substar.tial increases in flood heights. Minimum Federal standards Umi t such increases to 1.0 foot, provided that hazardous velocities are not produced. The floodways in this study are presented to local agencies as minimu~ standards that can be adopted directly or that can be ".ed '13 " basis for additional flocdway studies. The Hoodways presented in this study were computed far c"rtai~. st ream segment So on the bas i s :)f eQua 1 c0nveyance ['educt il)n ::: rom e""h side of the fl )~dpLa.Ln. Floodway widths were computed at ~rass sections. Between cross sections, the floodway boundaries "~-e interpolated. ThE results of the floodway computations are tabulated at selected cross sections (Table 3), In cases wh~re t~~ -floodway and lOO-year floodplain boundaries are either cicse together or collinear, only the floodway boundary tas been sho"~. The area between the floodway and lOO-year floodplain boundaries '5 termed the floodway f~inge. Th" floodway fringe encompasses the rortion of (he floodplain that could be co~pletely obstructed without increasing the water-s~~face elevation of the IOO-year flood more than 1.0 foot at any point. Typica~ relationships between the fl_oedway and the floodway fringe and cheir sign i fieanee to flOOdplain development are shown in F,-gure 2. }4