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<br />remains, however, because of inadequate channel, culvert, and <br />bridge capacities through the city. The channels must accommodate <br />reservoir release water and runoff from areas below the dams. <br /> <br />A watershed project was planned for the upper reaches of Big Sandy <br />Creek in 1957 (Reference 4). Construction of Big Sandy Creek <br />project was completed in 1966. This project provides flood protec- <br />tion to the towns of Ramah and Simla and reduces damage to agricul- <br />ture lands along the upper reach. The influence of this project <br />is lost, however, as the contributing drainage area increases <br />below the project. <br /> <br />~ <br /> <br />Potential flood damage to existing development and possible loss <br />of life can be alleviated or lessened through several nonstructural <br />and structural methods. Nonstructural methods include: flood <br />plain regulations, land treatment, flood warning and forecasting <br />systems, flood insurance, flood proofing, and flood fighting and <br />emergency evacuations. <br /> <br />The National Oceanic and Atmospheric Administration, through its <br />National Weather Service, maintains year-round surveillance of <br />weather and flood conditions. Daily weather forecasts are issued <br />through the National Weather Service and disseminated by radio <br />and television stations. A general alert to the danger of flash <br />flooding is one of the services provided by the National Weather <br />Service. <br /> <br />3.0 ENGINEERING METHODS <br /> <br />For the flooding sources studied in detail in the community, standard <br />hydrologic and hydraulic study methods were used to determine the flood <br />hazard data required for this study. Flood events of a magnitude which <br />are expected to be equaled or exceeded once on the average during any <br />10-, 50-, 100-, or 500-year period (recurrence interval) have been selected <br />as having special significance for flood plain management and for flood <br />insurance rates. These events, commonly termed the 10-, 50-, 100-, <br />and 500-year floods, have a 10, 2, 1, and 0.2 percent chance, respectively, <br />of being equaled or exceeded during any year. Although the recurrence <br />interval represents the long term average period between floods of a <br />specific magnitude, rare floods could occur at short intervals or even <br />within the same year. The risk of experiencing a rare flood increases <br />when periods greater than 1 year are considered. For example, the risk <br />of having a flood which equals or exceeds the 100-year flood (1 percent <br />chance of annual exceedence) in any 50-year period is approximately <br />40 percent (4 in 10), and, for any 90-year periQd, the risk increases <br />to approximately 60 percent (6 in 10). The analyses reported herein <br />reflect flooding potentials based on conditions existing in the community <br />at the time of completion of this study. Maps and flood elevations <br />will be amended periodically to reflect future changes. <br /> <br />7 <br />