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county at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish peak discharge- frequency relationships for each flooding source studied in detail affecting the community. The peak discharge-frequency relationships utilized within this study for Ralston, Van Bibber, and Leyden Creeks, were obtained from the previously mentioned Major Drainageway Planning Report (Reference 1). The peak flows associated with Little Dry Creek and its tributaries can be obtained from the report entitled Flood Hazard Area Delineation. Little Drv Creek, (Reference 2). The peak discharges for each flooding source studied in detail affecting the City of Arvada, Colorado, are shown in Table 1. The flows presented 1n the Major Drainageway Planning Report (Reference 1) were generated using the Massachusetts Institute of Technology Catchment Program (MITCAT). The flows reported wi thin the study represented 2-, 5-, 10-, and 100-year return frequencies. Assurances could not be made by the City of Arvada that Leyden Lake would continue to be maintained and operated. Arvada Reservoir is a drinking water storage facility with its water level maintained at maximum elevation, thereby negating any flood routing ability. The peak flows used in the floodplain analysis do not represent any routing and resultant flood attentuation through these two reservoirs. However, assurances were made for the other previously mentioned reservoirs, and therefore, the floodflows were routed through those reservoirs. Since Ralston, Van Bibber, and Leyden Creeks were partial detailed studies based upon the Major Drainageway Planning Report, the flows used in the hydraulic analysis were in accordance with the flows used in that report. Furthermore, many of these flows are based upon ultimate basin conditions in accordance with reasonable projections of land use by Jefferson County and the City of Arvada. The use of future floodflows is standard procedure for the UDFCD. On Van Bibber Creek, the flows were based on present basin development conditions as of 1984. It should be noted that a relatively minor difference exists between future and existing flows on this creek. This is due largely to the fact that much of the basin is already developed. On Leyden Creek, the flows were based upon future basin development conditions without Leyden Lake in place. Since the flows for the 50- and 500-year events were not reported in the Major Drainageway Planning Study, it was necessary to interpolate and extrapolate these flows from the known flows at various design points. The extrapolation and interpolation of 6