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Belleview Avenue were used to determine starting water-surface elevations for Greenwood Gulch. The starting elevations for Prentice Gulch were taken from the Greenwood Gulch profiles at the confluence. Starting water-surface elevations on Goldsmith Gulch were estimated from normal depth computations at a section 1000 feet downstream of the Greenwood Village corporate limits for the 10-, 50-, and 500- year profiles, The 100-year elevation was taken directly from the Urban Drainage and Flood Control District Report at the same section (Reference 2). On Goldsmith Gulch, water-surface elevations for the 10- and 100- year floods were taken from reservoir routing computations also developed in the Flood Hazard Area Delineation Report (Reference 2). Elevations for the 50- and SOO-year floods were determined by straight-line extrapolation of the 10- and lOa-year water levels. All elevations are referenced to the National Geodetic vertical Datum of 1929 (NGVD), Elevation reference marks used in the study are shown on the maps. The hydraulic analyses for this study are based only on the effects of unobstructed flow. The flood elevations as shown on the profiles are thus considered valid only if hydraulic structures operate properly and do not fail. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS A prime purpose of the National Flood Insurance Program is to encourage state and local governments to adopt sound flood plain management pro- grams. Each Flood Insurance Study, therefore, includes a flood boundary map designed to assist communities in developing sound flood plain manage- ment 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 Insurance Administration as the base flood for purposes of flood plain manage- ment measures, The SOO-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 the SOO-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 1:6000, with a contour interval of 2 feet (References 1, 2, 3, and 4), In cases where the 100- and the SOO-year flood boundaries are close together, only the 100-year boundary has been shown. 7