Scouring at Bed Sills as a Response to Flash Floods
Publication: Journal of Hydraulic Engineering
Volume 135, Issue 6
Abstract
The temporal development of clear-water local scour depth at bed sills in uniform gravel beds is considered. Experiments are presented on the development of scour holes under unsteady hydraulic conditions, with the triangular-shaped hydrographs tested being of different durations and different rates of flow variation. Based on the experimental results and a theoretical framework, a method is given for the definition and prediction of the scouring process under unsteady flows in terms of a dimensionless temporal parameter. A “flash flood” is here defined as an event for which the scour doesn’t attain its potential magnitude, i.e., the equilibrium value for the peak hydrograph flow rate. This flood nature is dependent on both the characteristics of the flood event itself and the characteristics of the stream. A quantitative measure of what constitutes a flash flood is given in terms of the identified temporal parameter. Results show that the ratio between the final scour depth and the potential scour depth at a bed sill for a given hydrograph can be estimated as a function of the identified temporal parameter.
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Acknowledgments
Data analysis was funded by the PRIN project “Models and measurements of flow-sediment interactions at spatial and temporal scales of physical interest” of the Italian Ministry for Education and Scientific Research. The participation of the first writer in the experimental phase was supported through a scholarship offered by the “Ing. Aldo Gini” Foundation. The writers would like to thank Geoff Kirby who lead the instrumentation design, and who took part in setting up and carrying out the experiments.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 135 • Issue 6 • June 2009
Pages: 466 - 475
Copyright
© 2009 ASCE.
History
Received: Oct 29, 2007
Accepted: Nov 24, 2008
Published online: Feb 5, 2009
Published in print: Jun 2009
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