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attributable to flooding might be temporary evacuation of some areas, eroded streambanks, and flood fighting and post-flood cleanup and restoration. The Colorado River has a long history of snowmelt flooding, but due to the rural nature of the region, detailed information on flood events in the study area is not available. The first flood of record on the Colorado River in the study area occurred in June and July 1884. .. Other floods on the river were recorded in 1917, 1920, 1921, 1935, 1952, and 1957. The 1884 flood is generally considered the most severe known in the Palisade area. It resulted from rapid melting of a deep snowpack and concurrent heavy rains. 2.4 Flood Protection Measures There are no flood-control projects that have an effect in the study area. Reservoirs in the Colorado River Basin above the study area are operated for water conservation purposes and conse- quently provide 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. Palisade has a zoning ordinance, but it does not address flood hazards. 3.0 ENGINEERING METHODS For the flooding sources studied in detail in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magnitude 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 significance for flood plain management and for flood insurance rates. These events, commonly termed the 10-, 50-, 100-, and 300-year floods, have a 10, 2, 1, and 0.2 percent chance, respectively, of being equaled or exceeded during any year. Although the recurrence interval represents the long term average 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), and, 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. 5