Flood Hazard Delineation on Alluvial Fans

by Thomas R. Grindeland, Simons, Li & Associates Inc, Fort Collins, United States,
J. S. O'Brien, Simons, Li & Associates Inc, Fort Collins, United States,
Ruh-Ming Li, Simons, Li & Associates Inc, Fort Collins, United States,



Document Type: Proceeding Paper

Part of: Hydraulics/Hydrology of Arid Lands (H²AL)

Abstract: Alluvial fans are significant geomorphic features of arid lands. The unconfined and dynamic nature of alluvial fans makes standard methods of delineating flood hazards unsuitable. The probabilistic method suggested by the Federal Emergency Management Agency (FEMA) is currently the recognized means of assessing the flood-hazard potential of alluvial fans. The FEMA method, however, has limitations relative to its inherent assumptions. An alternative approach to delineating the flood hazards on alluvial fans utilizing two-dimensional numerical modeling has been developed and applied. Unlike the probabilistic method, the effect of existing developments and flood-control facilities on flow characteristics can be directly analyzed using this approach. The subjective interpretation of the effect of topographic or structural features on the fan is minimized.

Subject Headings: Alluvial channels | Flood plains | Federal government | Arid lands | Probability | Two-dimensional models

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