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| Titel |
Time-variant risk assessment of a hazard cascade at the example of a rockslide dam - a case study in the Upper Val Venosta / Vinschgau Valley, Italy |
| VerfasserIn |
Christian Kofler, Kathrin Renner, Francesco Comiti, Bernhard Gems, Stefan Schneiderbauer, Benni Thiebes, Romy Schlögel |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137505
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| Publikation (Nr.) |
 EGU/EGU2017-234.pdf |
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| Zusammenfassung |
| Earthquakes and heavy precipitation events represent the main triggering factors of mass
movements such as landslides, rockslides or debris flows. The overall hazard potential is
increased significantly if the mass movement subsequently interacts with an adjacent river
course by creating a fully or partially blockage of the channel. These temporary
dams can cause disastrous secondary hazards by backwater inundation or outburst
floods. Therefore, the formation and failure of rockslide dams can be regarded and
assessed as a cascade of hazards. Through the cascading effects, rockslide dams
can affect areas at great distances up –or downstream of the site where the actual
mass movement occurred. Moreover, the time span between the generation and
the failure of a rockslide dam can vary from few minutes to several days or even
decades. This type of cascading hazard is therefore subject to high temporal and spatial
variability. Due to the difficulties assessing the probabilities of each part of the hazard
cascade, there is a substantial uncertainty involved in the assessment of the overall
hazard.
Risk assessments, however, often do not account for this complexity when assessing the
exposed elements. Especially the exposure of people, highly mobile in space and time, is
often not taken into consideration. In this study, we propose a novel approach that combines
both the dynamic components of the hazard and the exposure.
The study area extends over the two municipalities of Stilfs/Stelvio and Prad am
Stilsferjoch/Prato allo Stelvio in the Autonomous Province of Bozen/Bolzano (South Tyrol)
in Northern Italy. Both municipalities are major tourist destinations in the region featuring
two ski resorts, a national park and the well-known ’Stilfser Joch/Passo dello Stelvio’
mountain pass. This implies a high daily and seasonal fluctuation of people, including
commuters and tourists.
The upper part of the slope above the village of Trafoi is at risk of a sudden
failure of a large rock slide mass. Previous works modelled various slope failure
scenarios and predicted rockslide run-out depositions of up to 75 m height in the
channel of the Trafoi River. In this work, firstly the hazard induced by a potential
rockslide dam was quantified. The backwater inundation was assessed by a GIS-based
method and the downstream flood event was modelled with a combined 1D-2D
hydrodynamic model. Secondly, the number of exposed people was estimated by a
grid-based population model capable to simulate daily or seasonal movement patterns of
people.
Results show that peak discharge out of the breaching rockslide dam can reach up to 2550
m3s−1. Population modelling reveal that around 6640 people would be exposed to this hazard
in winter time and 7250 in summer time. About one third of the persons would be tourists and
one fourth were local commuters. |
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