Evaluating Flood Hazards on Alluvial Fans

by Muna E. Faltas, Michael Baker Jr Inc, United States,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract: In 1982, the Federal Emergency Management Agency (FEMA) developed a methodology for the determination of flood hazard zones and base (100-year) flood elevations on alluvial fans for administering the floodplain management and insurance aspects of the National Flood Insurance Program. The FEMA methodology incorporates several hydraulic and hydrologic assumptions. In arid and semi-arid areas, long-term stream gaging records may not exist, and alternative means of estimating flood flow discharge-frequency at the apex must be utilized. This paper addresses the great variability associated with skew coefficients estimated from small samples of floodflow discharges and the resulting variability in estimated fan widths corresponding to a certain flood depth and velocity.

Subject Headings: Floods | Federal government | Water discharge | Management methods | Alluvial channels | Insurance | Arid lands

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