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chance floodplain boundaries have been delineated using the flood determined at each cross section. 4.2 Between cross sections, the boundaries were interpolated using topogra~ at a scale of 1:4,800, with a contour interval of 2 feet and 10 feet NGVI Canyon Creek (U.S. Army Corps of Engineers, September 1978). To~ maps at a scale of 1:2,400, with a contour interval of 2 feet were usE Mancos River, through the Town of Mancos, and Chicken Cree~ Engineering, March 1982). The City of Cortez Studies floodplain b were interpolated between cross sections based on 2-foot contour mapp Engineering, October 2005). For the Dolores River, West Dolores l Mancos River (upstream and downstream of the Town of Mancos floodplain boundaries between cross sections were interpolated using based on a triangulated irregular network or TIN (U.S. Army Corps of F Sacramento District, August 2005 and Anderson Consulting Engine August 2006 respectively). The 1-percent and 0.2-percent annual chance floodplain boundaries are the FIRM (Exhibit 2). On this map, the 1-percent annual chance boundary corresponds to the boundary of the areas of special floc (Zones A AE, AH, AO, AR, A99, and D), and the 0.2-percent anni floodplain boundary corresponds to the boundary of areas of mode hazards. In cases where the 1-percent and 0.2-percent annual chance boundaries are close together, only the 1-percent annual chance floo been shown. Small areas within the floodplain boundaries may lie flood elevations but cannot be shown due to limitations of the map sc lack of detailed topographic data. For the streams studied by approximate methods, only the 1-pe~ chance floodplain boundary is shown on the Flood Insurance (Exhibit 2). Floodways Encroachment on floodplains, such as structures and fill, reduces floo~ capacity, increases flood heights and velocities, and increases flood t areas beyond the encroachment itself. One aspect of floodplain ma involves balancing the economic gain from floodplain development a resulting increase in flood hazard. For purposes of the NFIP, a floodw as a tool to assist local communities in this aspect of floodplain ma~ Under this concept, the area of the 1-percent annual chance floodplain into a floodway and a floodway fringe. The floodway is the channel of plus any adjacent floodplain areas, that must be kept free of encroachmE the 1-percent annual chance flood can be carried without substantial in flood heights. Minimum Federal standards limit such increases to provided that hazardous velocities are not produced. The floodways in nic maps for Lost ~ographic d for the (Muller -undaries ng (Goff .iver and studies, GeoRAS ngineers, ~rs, Inc., ~hown on .oodplain hazards ~1 chance ~te flood ~oodplain plain has bove the le and/or it annual ate Map in nst the is used divided stream, so that ;ases in .0 foot, is study 16