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boundaries of this flooding were taken from the previous COE study (Reference 1). The 100-year flood plain for and downstream of Lake Minnequa was delineated on topographic maps at a scale of 1:4,800, with a contour interval of 2 feet (Reference 14) based on the shallow-flooding depths determined as discussed in Section 3.2 and on field inspection. The Arkansas River approximate flood plain boundaries were delineated on topographic maps at a scale of 1:1,200, with a contour interval of 2 feet (Reference 23) and the 1:24,000-scale topographic maps discussed previously (Reference 21). Approximate flood plain boundaries for Fountain Creek were taken from a Flood Prone Area Map prepared by the USGS (Reference 24). Approximate flood plain boundaries for University Park Tributary were delineated on the 1:2,400 scale topographic map described previously (Reference 18). Approximate flood plain boundaries for Dry Creek (East) upstream from 4th Street were delineated on the 1:24,000-scale topographic maps described previously (Reference 21), supplemented by construction plans for State Highway 47 (Reference 25). Downstream of 4th Street, approximate flood plain boundaries were taken from the Flood Hazard Map for Pueblo County (Reference 26). Approximate 100-year flood plain boundaries in some portions of the study area were taken directly from the Flood Insurance Rate Map (Reference 27). 4.2 Floodways Encroachment on flood plains, such as structures and fill, reduces flood-carrying capacity, increases flood heights and velocities, 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 NFIP, 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 plain is divided into a floodway and a floodway fringe. The flood- way is the channel of a stream, plus any adjacent flood plain areas, that must be kept free of encroachment so that the 100-year flood can be carried without substantial increases in flood heights. Minimum Federal standards limit such increases to 1.0 foot, provided that hazardous velocities are not produced. The floodways in this study are presented to local agencies as minimum standards that can be adopted directly or that can be used as a basis for additional floodway studies. 22