Experimental Steep, Braided Flow: Application to Flooding Risk on Fans
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Volume 128, Issue 3
Abstract
Flooding processes occurring on alluvial fans are considerably different from those occurring along single thread rivers with well defined floodplains. Active erosion, rapid sedimentation, and the uncertainty in flow path make the prediction of flood evolution and extent difficult. Based on a large scale experiment, this study investigates the long term evolution of the flow on a steep, noncohesive sediment surface resembling a complex of merged alluvial fans. The results are pertinent to the assessment of flooding hazard on alluvial fans. At any given time, the average flow occupancy was 21% of the surface. However, the flow was characterized by active channel switching and overflow processes. The percentage of the surface remaining dry was found to decay harmonically with time. A reworking time was defined as the time at which half of the surface that was initially dry remained dry, whereas the other half was inundated at least once. An empirical expression was developed in which reworking time is proportional to the average cross sectional area of flow and inversely proportional to the sediment supply.
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Published In
Journal of Hydraulic Engineering
Volume 128 • Issue 3 • March 2002
Pages: 322 - 330
Copyright
Copyright © 2002 American Society of Civil Engineers.
History
Received: Oct 12, 2000
Accepted: Aug 14, 2001
Published online: Mar 1, 2002
Published in print: Mar 2002
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