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| Titel |
Impact of rainfall and snowmelt on unstable slope destabilisation using wavelet analysis (Séchilienne, French Alps) |
| VerfasserIn |
Aurélien Vallet, Jean-Baptiste Charlier, Marie-Aurélie Chanut, Catherine Bertrand, Jacques Mudry |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074178
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| Zusammenfassung |
| Increase of pore water pressure in hillslopes after rain events is one of the main triggering
factors of deep seated landslides. To our knowledge, few investigations have been carried out
yet to understand relationships between precipitation amount and unstable slope
destabilization on long time series (> several years). Wavelet analysis has become a powerful
technique to investigate the variability of hydrological response (rainfall-discharge
relationships). Decomposing a time series into time-frequency space, this method
localizes power variations within a time series. It is ideal for analyzing non-stationary
signals and identifying short- to long-term periodic phenomena. In this setting, we
hypothesis that wavelet was a pertinent tool to characterize precipitation-displacement
relationships on unstable slopes. Using wavelet analysis, this work aims to characterize the
impact of precipitation on unstable slope displacement in a mountainous area where
snowmelt is an important component of the annual water balance. The study site is
the Séchilienne deep seated unstable slope located in French Alps. The unstable
slope is monitored at a daily rate since about 20 years, by several displacement
stations and a meteorological station which allows estimating rainfall and snow melt
amount. A strong spatial heterogeneity for displacements intensity and direction with
zones more active than others is observed. We applied wavelet analysis on the two
recharge components (i.e., rainfall and snowmelt) and on two displacement stations in
order to compare the spatial variability of recharge influence in the two main slope
destabilization zones. The main results show that rain and snowmelt components have
a different influence on the destabilization, and that only the most active zone is
sensitive to recharge variations. We showed that there was an evolution of slope
displacement, especially in the last 4 years with a strong velocity increase. In the most
active zone, displacement was affected slightly at a short time scale (< several
months) by main rainfall events, and was highly impacted by snowmelt at an annual
scale. In the last four years, snow melting was more important due to a pluri-annual
series of cold winter. From this date, rainfall impact on the destabilization begun
to be significant, meaning that a threshold may have been reached after series of
harsh winter allowing rainfall recharge to play also a role in the destabilization.
Consequently, from this analysis one may suppose that snow melt is the main key
process driving destabilization of the unstable slope. Finally, this study highlights
the effectiveness of wavelet analysis in characterizing destabilization of complex
unstable slopes with a naturally high level of non-linear hydrological behaviour. |
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