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In 1965, heavy rains and hail again destroyed many crops and homes, sending flows of water and mud into basements and living rooms. J:i0u~ing damages were reported to be in the thousands of dollars. 2.4 Flood Pro~ection Measures There are no proposed or existing flood protection structures which would reauce the flood hazards in the Town of Firestone. 3.U ENG~~~~~~N~~~THODS For the flooding sources s.tudied in detail in the community, st~ndard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magnitude which are exvccted to be equalled or exceeded once on the average during any 10-, 50-, 100-, or SOO-year period (recurrence interval) have been selected as having special significance for flood plain management and for flood insurance premium rates. These events, commonly ter~ed the 10-, SO-, 100-, and SOO-year floods, have a 10, 2, 1, and 0.2 percent chance, respectively, of being equalled 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 lOO-year flood (1 percent chance of annual occurrence) in any 50-year period is apvroximate1y 40 percent (4 in 10), and, for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported here 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 the peak discharge- frequency relationships for floods of the selected recurrence intervals for each stream studied in detail in the community. No streamflow gaging information is available for the Tri-Area Drainageway flowing through Firestone. Gaging information on ,mall watersheds in .Colorado is currently being collected by the State Highway Department, but records to date are sporadic, and the period of record is short. The U.S. Soil Conservation Service method for developing synthetic hydrographs was, therefore, used to determine frequency discharges in this basin (Reference 6). This method is particularly suited to small agricultural watersheds. Rainfall data used in the hydrologic analyses were obtained from the National Oceanic and Atmospheric Administration Atlas for Colorado (Refer- ence 7), atid soil and land use information was taken from maps prepared by the U.S. Soil Conservation Service (Reference 3). 4