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only incidental flood protection to the Palisade area. However, incidental storage, trans-mountain diversion, and irrigation uses have served, and will probably continue to serve, in reducing peak flows of very large floods in the study reach. Major reservoirs controlling the Colorado and Gunnison Rivers above the Town of Palisade are Granby, Green Mountain, Dillon, Williams Fork, Reudi, Taylor Park, Vega, Paonia, Morrow Point, and Blue Mesa. Floodplain regulations have been adopted by Palisade. Designated floodplains, including floodway zones, are incorporated into zoning maps. 3.0 ENGINEERING METHODS For the flooding sources studied by detailed methods in the cOllUDuni ty, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magni tude which are expected to be equaled or exceeded once on the average during any 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected as having special significsnce for floodplain management and for flood insurance rates. These events, cOllUDonly termed the 10-, 50-, 100-, and 500-year floods, have a 10, 2, 1 and 0.2 percent chance, respectively, of being equaled or exceeded during any year. Al though the recurrence interval represents the long- term, avera2e period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than 1 year are considered. For example, the risk of having a flood which equals or exceeds the 100-year flood (1 percent chance of annual exceedence) in any 50-year period is approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in the community 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 by detailed methods affecting the cOllUDunity. The discharge values used were based on the results of the 1985 COE hydrology report on the Colorado River from Glenwood Springs to DeBeque Canyon (Reference 4). A hydrology report dated May 1989 was prepared by J. F. Sato & Associates, Inc., (Reference 5). In this study the peak discharges along the Colorado River from DeBeque Canyon to the Utah State line were analyzed. 5