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Insurance Study includes a flood boundary map designed to assist communi- ties in developing sound flood plain management measures. 4.1 Flood Boundaries In order to provide a national standard without regional discrimina- tion, the 100-year flood has been adopted by the Federal Emergency Management Agency as the base flood for purposes of flood plain management meaSUres. The 500-year flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the 100- and 500-year floods have been delineated using the flood elevations determined at each cross section; between cross sections, the boundaries were interpolated using topographic maps at a scale of 1:2400, with a contour interval of 2 feet (Reference 7). Flood boundaries for the 100- and 500-year floods are shown on the Flood Boundary and Floodway Map (Exhibit 2). In cases where the 100- and 500-year flood boundaries are close together, only the 100-year flood boundary has been shown. Small areas within the flood boundaries may lie above the flood elevations and, there- fore, not be subject to flooding; owing to limitations of the map scale, such areas are not shown. 4.2 Floodways Encroachment on flood plains, such as artificial fill, reduces the flood-carrying capacity, increases the flood heights of streams, and increases flood hazards in areas beyond the encroachment itself. One aspect of flood plain management involves balancing the economic gain from flood plain development against the resulting increase in flood hazard. For purposes of the National Flood Insurance Programl the concept of a floodway is used as a tool to assist local communities in this aspect of flood plain management. Under this concept, the area of the 100-year flood is divided into a floodway and a floodway fringe. The floodway is the channel of a stream plus any adjacent flood plain areas that must be kept free of encroachment in order that the 100-year flood may be carried without substantial increases in flood heights. Minimum standards of the Federal Emergency Management Agency limit such increases in flood heights to 1.0 foot, provided that hazardous velocities are not produced. The floodways in this report are presented to local agencies as minimum standards that can be adopted or that can be used as a basis for additional studies. Floodways were also identified by the criterion that allows a maximum hazardous velocity of 3 feet per second at the edge of the floodway fringe. The hazardous velocity criterion proved to be determinant in the floodway delineation. For Bear Creek Tributary No, 7, the 100-year discharge is contained within the 15