Alluvial Fan Flooding

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The purpose of this page is to define Alluvial Fan Flooding, a commonly used term in floodplain management.


Flooding occurring on the surface of an alluvial fan or similar landform which originates at the apex and is characterized by high-velocity flows; active processes of erosion, sediment transport, and deposition; and unpredictable flowpaths. Alluvial fan flooding is depicted on a Flood Insurance Rate Map (FIRM) as Zone AO, with a flood depth and velocity.

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Last Updated: 
04/26/2015 - 13:09
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