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Rifle Creek overflows its western bank just upstream of County Highway 291. This overflow is referred to in this Flood Insurance Study as Rifle Creek Splitflow. A separate HEC-2 step-backwater analysis (Reference 6) was performed for the splitflow. Discharge values used in the step-backwater analysis were based on a hydraulic analysis of the overflow from the main channel of Rifle Creek. Cross sections were digitized from aerial photographs (Reference 9). Roughness factors for the channel ranged from 0.050 to 0.080, whereas 0.080 was used for the overbank value. The starting water-surface elevations were based on the computed water-surface elevations on Rifle Creek. A profile base line was used to establish the relative distance shown on the profile for Rifle Creek Splitflow. This profile base line is shown and identified on the maps. A culvert along Hubbard Gulch near 14th street obstructs the flow. Water leaves the channel along the east bank, causing shallow flooding in the vicinity of the Garfield County Fairgrounds. Alluvial fan methodologies were applied to calculate flow depths and velocities on Helmer and Ramsey Gulches (Reference 10). An approximate flood boundary was determined for Warmbroth Creek. The extent of the flood boundary was based on approximating normal depth and using the 100-year peak discharge. The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the profiles are thus con- sidered valid only if 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 this study are shown on the maps. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS The National Flood Insurance Program (NFIP) encourages state and local governments to adopt sound flood plain management programs. Therefore, each Flood Insurance Study produces maps designed to assist communities in developing flood plain management measures. 4.1 Flood Boundaries To provide a national standard without regional discrimination, the I percent annual chance (lOO-year) flood has been adopted by FEMA as the base flood for flood plain management purposes. The 0.2 percent annual chance (500-year) flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the 100- and 500-year flood plain boundaries have been delineated using the flood elevations determined at each 9