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| Titel |
On the role of the runoff coefficient in the mapping of rainfall to flood return periods |
| VerfasserIn |
A. Viglione, R. Merz, G. Blöschl |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 13, no. 5 ; Nr. 13, no. 5 (2009-05-12), S.577-593 |
| Datensatznummer |
250011858
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| Publikation (Nr.) |
 copernicus.org/hess-13-577-2009.pdf |
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| Zusammenfassung |
| While the correspondence of rainfall return period TP and flood return
period TQ is at the heart of the design storm procedure, their
relationship is still poorly understood. The purpose of this paper is to shed
light on the controls on this relationship examining in particular the effect
of the variability of event runoff coefficients. A simplified world with
block rainfall and linear catchment response is assumed and a derived flood
frequency approach, both in analytical and Monte-Carlo modes, is used. The
results indicate that TQ can be much higher than TP of the associated
storm. The ratio TQ /TP depends on the average wetness of the system. In a
dry system, TQ can be of the order of hundreds of times of TP. In
contrast, in a wet system, the maximum flood return period is never more than
a few times that of the corresponding storm. This is because a wet system
cannot be much worse than it normally is. The presence of a threshold effect
in runoff generation related to storm volume reduces the maximum ratio of
TQ /TP since it decreases the randomness of the runoff coefficients and
increases the probability to be in a wet situation. We also examine the
relation between the return periods of the input and the output of the design
storm procedure when using a pre-selected runoff coefficient and the question
which runoff coefficients produce a flood return period equal to the rainfall
return period. For the systems analysed here, this runoff coefficient is
always larger than the median of the runoff coefficients that cause the
maximum annual floods. It depends on the average wetness of the system and on
the return period considered, and its variability is particularly high when a
threshold effect in runoff generation is present. |
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