Redefining Terminology of Flood Exceedance Probabilities by Basic Counting
Publication: Journal of Hydrologic Engineering
Volume 21, Issue 10
Abstract
By convention, design discharge estimates are often expressed in terms of annual exceedance probability (AEP) or average recurrence interval (ARI). This paper describes the limitations of using AEP and ARI to reliably convey the expected incidence of flood magnitudes to decision makers and the public. An alternative expression—exceedance events per 1,000 years ()—is proposed, which offers a less ambiguous definition of design discharge frequency. A case is argued for the adoption of based on several perceived advantages to AEP and ARI, including (1) by definition, it is a measure of number of flood exceedances over a timespan but can also communicate shifts in flood frequency over time, (2) the results of analysis using peak-over-threshold and annual maximum series can be both presented on the same chart, and (3) as a probability-based expression can be easily converted to alternatives used in floodplain risk analysis.
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Information & Authors
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Published In
Journal of Hydrologic Engineering
Volume 21 • Issue 10 • October 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Jul 2, 2015
Accepted: Apr 12, 2016
Published online: Jun 8, 2016
Published in print: Oct 1, 2016
Discussion open until: Nov 8, 2016
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