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| Titel |
A 2600-year history of floods in the Bernese Alps, Switzerland: frequencies, mechanisms and climate forcing |
| VerfasserIn |
L. Schulte, J. C. Peña, F. Carvalho, T. Schmidt, R. Julia, J. Llorca, H. Veit |
| 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. 7 ; Nr. 19, no. 7 (2015-07-10), S.3047-3072 |
| Datensatznummer |
250120760
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| Publikation (Nr.) |
 copernicus.org/hess-19-3047-2015.pdf |
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| Zusammenfassung |
A 2600-year long composite palaeoflood record is reconstructed from
high-resolution delta plain sediments of the Hasli–Aare floodplain on the
northern slope of the Swiss Alps. Natural proxies compiled from sedimentary,
geochemical and geomorphological data were calibrated by textual and factual
sources and instrumental data. No fewer than 12 of the 14 historically
recorded extreme events between 1480 and the termination of the Hasli–Aare
river channel correction in 1875 were also identified by coarse-grained
flood layers, log(Zr / Ti) peaks and factor 1 anomalies. Geomorphological,
historical and instrumental data provide evidence for flood damage
intensities and discharge estimations of severe and catastrophic historical
floods.
Spectral analysis of the geochemical and documentary flood series and
several climate proxies (TSI, δ18O, tree-rings, NAO, SNAO)
identify similar periodicities of around 60, 80, 100, 120 and 200 years
during the last millennia, indicating the influence of the North Atlantic
circulation and solar forcing on alpine flood dynamics. The composite
floodplain record illustrates that periods of organic soil formation and
deposition of phyllosilicates (from the medium high catchment area) match
those of total solar irradiance maxima, suggesting reduced flood activity
during warmer climate pulses. Aggradation with multiple sets of flood layers
with increased contribution of siliciclasts from the highest catchment area
(plutonic bedrock) (e.g. 1300–1350, 1420–1480, 1550–1620, 1650–1720 and
1811–1851 cal yr AD) occurred predominantly during periods with reduced
solar irradiance, lower δ18O anomalies, cooler summer
temperatures and phases of drier spring climate in the Alps. Increased water
storage by glaciers, snow cover and snow patches susceptible to melting
processes associated with rainfall episodes and abrupt rises in temperature
substantially increased surface runoff on slopes and discharges of alpine
rivers. This interpretation is in agreement with the findings that the
severe and catastrophic historical floods in the Aare since 1670 occurred
mostly during positive SNAO (Summer North Atlantic Oscillation) pulses after years or even decades dominated by
negative SNAO and cooler annual temperatures. |
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