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<br />26 <br /> <br />ALLUVIAL FAN FLOODING <br /> <br /> <br />Alluvial fan <br />flooding <br /> <br />A <br /> <br />Flow path <br />uncertainty <br /> <br /> <br />B <br /> <br />Abrupt <br />deposition <br />and erosion <br /> <br />C <br />Inadequacy of <br />elevation on fill <br />as mitigation <br /> <br /> <br />Uncertain flow path <br />flooding <br /> <br />FIGURE 1-7 A, B, and C refer to the criteria in the committee's definition. <br /> <br />confinement and by the occurrence of erosion and deposition processes. Together, these <br />characteristics create a flood hazard that can be reliably mitigated only by the use of major <br />structural flood control measures or by complete avoidance of the affected area. <br />The potential for erosion and deposition, the related uncertainty in flow path behavior, and <br />the imprudence of elevation on fill as a mitigation measure are joint and separate characteristics <br />shared among many flood hazards on depositional environments other than alluvial fans, although <br />not usually with the same intensity. It stands to reason that some of the same rules that apply to <br />alluvial fan flooding should apply to this more inclusive type of flood hazard, termed UI/certain <br />flaw path flooding. Flood hazards that meet only one or two of the criteria in the definition make <br />up this third category. <br />To apply any definition in a regulatory context, the definition must be supported by criteria <br />that can serve as standards, principles, or tests. These criteria, as reflected in indicators such as <br />data, measurements, field evidence, and observations, are what floodplain managers and <br />