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Indian Wash ranged from 0.022 to 0.06 and in the flood plain from 0.03 to 0.09. The starting water-surface elevations for Colorado River, Leach Creek, and Horizon Drive Channel were obtained from the Mesa County, Colorado, Flood Insurance Study (Reference 1). Starting water- surface elevations for Indian Wash were estimated using a rating chart developed for the upstream side of the large culvert passing under the multiple tracks of the Denver & Rio Grande Western Rail- road near the south end of the study reach. Flood profiles were drawn showing computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals (Exhibit 1). The results obtained from the HEC-2 computer program were adjusted in the vicinity of bridges to represent more accurately the actual flooding conditions (Reference 11) . The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the flood profiles are, thus, considered valid only if the hydraulic structures remain unobstructed, operate properly, and do not fail. 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. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS The National Flood Insurance Program encourages State and local govern- ments to adopt sound flood plain management programs. Therefore, each Flood Insurance Study includes a flood boundary map designed to assist communities 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 an orthophoto topographic map at a scale of 1:2400, with a contour interval of 2 feet (Reference 10). 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 18