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| Titel |
A process-based model for the definition of hydrological alert systems in landslide risk mitigation |
| VerfasserIn |
M. Floris, A. D'Alpaos, A. de Agostini, G. Stevan, G. Tessari, R. Genevois |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 12, no. 11 ; Nr. 12, no. 11 (2012-11-14), S.3343-3357 |
| Datensatznummer |
250011194
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| Publikation (Nr.) |
 copernicus.org/nhess-12-3343-2012.pdf |
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| Zusammenfassung |
The definition of hydrological alert systems for rainfall-induced landslides is strongly related to a deep
knowledge of the geological and geomorphological features of the territory. Climatic conditions, spatial and
temporal evolution of the phenomena and characterization of landslide triggering, together with
propagation mechanisms, are the key elements to be considered. Critical steps for the development of the
systems consist of the identification of the hydrological variable related to landslide triggering and of the
minimum rainfall threshold for landslide occurrence.
In this paper we report the results from a process-based model to define a hydrological alert system for the
Val di Maso Landslide, located in the northeastern Italian Alps and included in the Vicenza Province
(Veneto region, NE Italy). The instability occurred in November 2010, due to an exceptional rainfall event
that hit the Vicenza Province and the entire NE Italy. Up to 500 mm in 3-day cumulated rainfall generated
large flood conditions and triggered hundreds of landslides. During the flood, the Soil Protection Division of
the Vicenza Province received more than 500 warnings of instability phenomena. The complexity of the
event and the high level of risk to infrastructure and private buildings are the main reasons for deepening
the specific phenomenon occurred at Val di Maso.
Empirical and physically-based models have been used to identify the minimum rainfall threshold for the
occurrence of instability phenomena in the crown area of Val di Maso landslide, where a retrogressive
evolution by multiple rotational slides is expected. Empirical models helped in the identification and in the
evaluation of recurrence of critical rainfall events, while physically-based modelling was essential to verify
the effects on the slope stability of determined rainfall depths. Empirical relationships between rainfall and
landslide consist of the calculation of rainfall Depth-Duration-Frequency (DDF) curves, which allow one to
determine rainfall depth (or intensity) as a function of duration for given return periods or probabilities of
exceedance (frequencies). Physically-based modelling was performed through coupled seepage and slope
stability analyses.
Combining results from empirical and physically-based modelling, the minimum alert threshold for a
reactivation of the phenomenon was found in rainfall cumulated up to 60 days with a return period of
2 yr. These results were used to set up a hydrological alert system based on the calibration of DDF curves
which can be used as a sort of abacus to plot in real time rainfall depths and to set increasing levels
of alert on the basis of the degree of exceptionality of rainfall.
The alert system for Val di Maso was successfully tested by the rainfall events that produced displacements
which have been recorded by extensometers placed in the crown area after the November 2010 landslide.
However, further tests are recommendable to improve the process-based model that led to the
implementation of the alert system. To this end, a monitoring system is currently being realized. In the
near
future, monitoring data will help in testing and improving landslide evolution and alert models.
The proposed hydrological alert system proves to be effective mainly because it can be applied to different
scales of investigation and geological and geomorphological contexts. In fact, it might also be applicable
to territorial scale analyses, as showed by the brief example provided in this paper on how the alert system
could be used for landslide early warning in the area surrounding Val di Maso. Furthermore, it is easy to set
up. The needed components are a rain gauge station, a software that compares rainfall data to rainfall
events with different return periods and degree of alert, and a transmission system of the warning levels to
authorities. |
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