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for floodplain management and for flood insurance rates. These events, commonly 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. Although the recurrence interval represents the long- term averaRe 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 one year are considered. For example, the risk of having a flood which equals or exceeds the 100-year flood (I 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 Flood Insurance Study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish the peak discharge-frequency relationships for each flooding source studied by detailed methods affecting the community. Peak discharges for the various recurrence intervals for Tomichi Creek and the Gunnison River were taken from data prepared by Engineering Consultants, Iuc. for the Gunnison River Basin near Gunnison, Colorado (Reference 2). Streamflow data obtained from 51 measuring stations located within the Gunnison River Basin and in nearby basins were used in this analysis. The source of the data is the official U.S. Geological Survey (USGS) Water Supply Papers (Reference 4). The peak flow figures for the four different frequencies used in the analysis of the two streams mentioned previously were those obtained from the Regional Log- Pearson Type III Analyses (Reference 5). Peak discharges for the various recurrence intervals for North Fork Gunnison River were taken from data prepared by the COE, Sacramento District. A flow-frequency analysis was made for four index points on the North Fork Gunnison River, with the upstream gaging station being the USGS gaging station near Somerset (Hydro- logic Unit 14020004; period of record: 1897 to 1933, 1934 to present day), and downstream points that reflect significant inflow. The source of the gaging data was the official USGS Water Supply Papers (Reference 4). Flow-frequency curves were developed from generalized frequency relationships estimated from a regional-frequency analysis of gaging stations, North Fork Gunnison River near Paonia gage (period of record: 1922-1932); Gunnison River below Gunnison Tunnel gage (Hydrologic Uni t 14020002; period of record: 1903 to present day); and Gunnison River near Grand Junction gage (Hydro- 7