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Figure 6.2 <br /> Flood Return Period vs. First Floor Elevation <br /> <br /> Flood Frequency vs. First Floor Elevation <br /> <br /> 400 <br /> <br /> 300 <br /> <br /> 250 <br /> <br /> 100 <br /> <br /> 434 435 436 437 438 439 440 441 442 443 <br /> <br /> First Floor Elevation (feet) <br /> <br /> 6,3.4 Caveats for the Eugene/Springfield Metro Area Flood insurance <br /> Study <br /> <br />The Flood insurance Study (FIS) for the Eugene/Springfield Metro Area is relatively <br />recent (June 2, 1999), although much of the data is from older sources. Flood <br />insurance Studies, FiRM maps, and flood hazard data are a snapshot in time and <br />cannot take into account development or other watershed changes that may occur <br />subsequent to the study date for a FIS. <br /> <br />Flood hazard data change with time as channels and watersheds evolve with <br />increasing development and other changes. Increasing development often increases <br />runoff and increases flood discharges and elevations. Over time, the accuracy of an <br />FIS typically diminishes and any FIS should be redone periodically to ensure that data <br />are accurate and up to date for flood zoning and mitigation planning purposes. Simply <br />because an FIS is old, does not necessarily mean that a FIS is outdated or inaccurate. <br />However, the older a study is, and the more development that has occurred within the <br />watershed, the more likely it is that channel or watershed conditions have changed <br />over time. Therefore, as time passes, care should be taken in interpreting and using <br />data from the FIS, especially in reaches of rivers or streams where substantial <br />channel changes are documented or flood control measures have been added. Over <br /> <br />Public Review Draft: August 6, 2004 <br /> <br /> <br />