Entrenched Channels and Alluvial Fan Flooding

by Edward R. Mifflin, Michael Baker, Jr., Inc., Alexandria, United States,

Document Type: Proceeding Paper

Part of: Hydraulics/Hydrology of Arid Lands (H?AL)


Because the individual flood paths on alluvial fans are unpredictable, determining flood hazards on such landforms is hindered by particular complications. The proper framework in which to make such determinations was presented by D.R. Dawdy in 1979. Subsequent to that publication, the Federal Emergency Management Agency [FEMA, 1985] adopted the methodology proposed by Dawdy to advance their efforts in showing flood hazard areas on Flood Insurance Rate Maps (FIRMs). As more alluvial fans were modeled, it became more apparent that in some cases, as Dawdy had cautioned, the site-specific conditions did not adhere to the simple boundary conditions set forth in Dawdy's paper. This paper was written to demonstrate that considering one such condition, the presence of an entrenched channel, does not preclude the use of Dawdy's methodology, but rather attests to its versatility.

Subject Headings: Floods | Alluvial channels | Natural disasters | Management methods | Federal government | Water flow | Water discharge

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