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| Titel |
Flood frequency analysis of historical flood data under stationary and non-stationary modelling |
| VerfasserIn |
M. J. Machado, B. A. Botero, J. Lopez, F. Francés, A. Diez-Herrero, G. Benito |
| 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 ; 19, no. 6 ; Nr. 19, no. 6 (2015-06-02), S.2561-2576 |
| Datensatznummer |
250120727
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| Publikation (Nr.) |
 copernicus.org/hess-19-2561-2015.pdf |
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| Zusammenfassung |
| Historical records are an important source of information on
extreme and rare floods and fundamental to establish a reliable flood return
frequency. The use of long historical records for flood frequency analysis
brings in the question of flood stationarity, since climatic and land-use
conditions can affect the relevance of past flooding as a predictor of
future flooding. In this paper, a detailed 400 yr flood record from the
Tagus River in Aranjuez (central Spain) was analysed under stationary and
non-stationary flood frequency approaches, to assess their contribution
within hazard studies. Historical flood records in Aranjuez were obtained
from documents (Proceedings of the City Council, diaries, chronicles,
memoirs, etc.), epigraphic marks, and indirect historical sources and
reports. The water levels associated with different floods (derived from
descriptions or epigraphic marks) were computed into discharge values using
a one-dimensional hydraulic model. Secular variations in flood magnitude and
frequency, found to respond to climate and environmental drivers, showed a
good correlation between high values of historical flood discharges and a
negative mode of the North Atlantic Oscillation (NAO) index. Over the
systematic gauge record (1913–2008), an abrupt change on flood magnitude was
produced in 1957 due to constructions of three major reservoirs in the Tagus
headwaters (Bolarque, Entrepeñas and Buendia) controlling 80% of the
watershed surface draining to Aranjuez. Two different models were used for
the flood frequency analysis: (a) a stationary model estimating statistical
distributions incorporating imprecise and categorical data based on maximum
likelihood estimators, and (b) a time-varying model based on "generalized
additive models for location, scale and shape" (GAMLSS) modelling, which
incorporates external covariates related to climate variability (NAO index)
and catchment hydrology factors (in this paper a reservoir index; RI). Flood
frequency analysis using documentary data (plus gauged records) improved the
estimates of the probabilities of rare floods (return intervals of 100 yr
and higher). Under non-stationary modelling flood occurrence associated with
an exceedance probability of 0.01 (i.e. return period of 100 yr) has changed
over the last 500 yr due to decadal and multi-decadal variability of the
NAO. Yet, frequency analysis under stationary models was successful in
providing an average discharge around which value flood quantiles estimated
by non-stationary models fluctuate through time. |
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