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(FHBM) of February 11, 1977 (Reference 2). The 1977 FHBM was replaced with the current FIRM. Along the lower reaches of Forked Gulch, 500 feet above the confluence with the Arkansas River, Canon City has constructed a concrete lined channel to stabilize the banks to prevent further destruction of the Griffin Avenue Bridge. The City of Canon City has also adopted an ordinance regulating development in the flood plain (Reference 5). 3.0 ENGINEERING METHODS For the flooding sources studied by detailed methods 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 that is 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 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, 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 that equals or exceeds the 1-percent-annual-chance flood 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 each community. A regional relationship of basin area to peak discharge was used for the Arkansas River. Gaging stations located within the upper Arkansas Basin were used to determine the flood flow-frequency relationship based on a log-Pearson Type III distribution for each selected gaging station. The annual peak discharges were obtained from USGS Water-Supply Paper Nos. 1681, 1921, and 2121 (References 6-8,) and from Water Resources Data for Colorado (Reference 9). Regional relationships of basin area to peak discharge were determined for the 10-, 2-, 1- and 0.2-percent-annual-chance floods (Reference 10). Previously, the USACE, Albuquerque District, computed frequency-discharge curves from gage station analyses of the USGS gages on the Arkansas River at Pueblo and Canon City, USGS gage stations 70960 and 70995, respectively, (Reference 11). A Log-Pearson Type-II fit was utilized at each station. The results for each frequency were then plotted with respect to drainage area (3,117 square miles at the Canon City gage, and 4,666 square miles at the Pueblo gage), and peak discharges for the Arkansas River at Colorado Highway 7