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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 lO-, 50-, lOO-, and 500-year period (recurrence interval) have been selected as having special significance for floodplain management and for flood insurance rates. These events, commonly termed the 10-, 50-, 100-, and 500-year floods, have a 10-, 2-, l-, and 0.2-percent chance, respectively, of being equaled or exceeded during any year. Al though the recurrence interval represents the long- term average period between floods of a specific magnitude, rare floods could occur at shart 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 lOO-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 ri sk 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.l Hydrologic Analyses Hydrologic analyses discharge-frequency by detailed methods were carried out relationships for each affecting the community. to establish the peak flooding source studied Peak floodflows on the White River were computed from a statistical analysis of 73 years of gaged data. A log-Pearson Type III fre- quency distribution was used in the analysis and three sets of discharges were computed from a station skew~ a regional skew, and a weighted skew coefficient. For further comparisons, a set of discharges was computed from a Gumbel extreme value distribution and Hazen plotting positions for the 66-year period of record from 1910 to 1976. Separation of the gaged data into snowmelt and rainfall categories was not considered. Several forms of regional comparisons were made as an aid in evaluating and interpreting the statistical flood frequency analysis. These include flood discharges calculated from regional multiple regression equations (TM-1, Reference 3), the index flood method (WSP l683, Reference 4), and comparisons with runoff (CSM) ratios for adopted 100-year frequency flood discharges in northwest Colorado. The hydrologic analysis for the White River near Rangely was based on annual peak flow data for snowmel t and rainfall floods. Annual peak flows for rainfall and snowmelt floods have been published by the USCS (Reference 5). Additional annual peak flows, for rainfall and snowmelt floods were obtained from inspection of the USGS strip charts. Frequency analyses were made on both peak flow data set s. 6