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| Titel |
Derivation and evaluation of landslide-triggering thresholds by a Monte Carlo approach |
| VerfasserIn |
D. J. Peres, A. Cancelliere |
| 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 ; 18, no. 12 ; Nr. 18, no. 12 (2014-12-08), S.4913-4931 |
| Datensatznummer |
250120549
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| Publikation (Nr.) |
 copernicus.org/hess-18-4913-2014.pdf |
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| Zusammenfassung |
Assessment of landslide-triggering rainfall thresholds is useful for early
warning in prone areas.
In this paper, it is shown how stochastic rainfall models and hydrological
and slope stability physically based models can be advantageously combined in
a Monte Carlo simulation framework to generate virtually unlimited-length
synthetic rainfall and related slope stability factor of safety data,
exploiting the information contained in observed rainfall records and
field-measurements of soil hydraulic and geotechnical parameters. The
synthetic data set, dichotomized in triggering and non-triggering rainfall
events, is analyzed by receiver operating characteristics (ROC) analysis to
derive stochastic-input physically based thresholds that optimize the
trade-off between correct and wrong predictions. Moreover, the specific
modeling framework implemented in this work, based on hourly analysis,
enables one to analyze the uncertainty related to variability of rainfall
intensity within events and to past rainfall (antecedent rainfall). A
specific focus is dedicated to the widely used power-law rainfall
intensity–duration (I–D) thresholds.
Results indicate that variability of intensity during rainfall events
influences significantly rainfall intensity and duration associated with
landslide triggering. Remarkably, when a time-variable rainfall-rate event is
considered, the simulated triggering points may be separated with a very good
approximation from the non-triggering ones by a I–D power-law equation,
while a representation of rainfall as constant–intensity hyetographs
globally leads to non-conservative results. This indicates that the I–D
power-law equation is adequate to represent the triggering part due to
transient infiltration produced by rainfall events of variable intensity and
thus gives a physically based justification for this widely used threshold
form, which provides results that are valid when landslide occurrence is
mostly due to that part. These conditions are more likely to occur in
hillslopes of low specific upslope contributing area, relatively high
hydraulic conductivity and high critical wetness ratio. Otherwise, rainfall
time history occurring before single rainfall events influences landslide
triggering, determining whether a threshold based only on rainfall intensity
and duration may be sufficient or it needs to be improved by the introduction
of antecedent rainfall variables. Further analyses show that predictability
of landslides decreases with soil depth, critical wetness ratio and the
increase of vertical basal drainage (leakage) that occurs in the presence of
a fractured bedrock. |
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