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Infrastructure Resilience Conference 2018

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Road Network Sensitivity to floods

Settlements in remote mountainous areas are often only accessible by roads. Hence, the road network is crucial for the supply to these areas and the access roads are commonly defined as lifelines. In case of extreme flood or snow avalanche events, an interruption of these access roads leads to a temporary isolation of the settlements in the valley heads. The supply to a minor number of cut off settlements is ensured by temporary helicopter operations. However, resources for such operations are limited and in case of increasing numbers of isolated people, the supply cannot be guaranteed anymore.

We assume that extreme precipitation events cover a wide range in the number and area of affected catchments. Here, we study the relationship between the size of the area affected by floods and snow avalanches (process areas within headwater catchments) and the number of isolated people. For this purpose, we set up a road network model for Switzerland with the exposure of the network edges against these processes and the ability to compute the interdependencies between the nodes. Cantonal and national hazard maps are considered for the exposure analysis. We use Monte-Carlo simulations to distribute spatially the extreme precipitation events, which cause floods and avalanches and calculate the number of isolated people due to road disruptions. The main question is how the number of isolated people grows with an increasing number and area of affected catchments. This analysis shows that the organization of temporary flight bridges becomes incrementally challenging with the increasing extension of an extreme precipitation event and that alternative supply concepts are needed. The results support the decisions in the preparedness planning of civil protection services and thus help to enhance the robustness of the supply system in general and the resilience of the remote areas in particular.

Veronika Röthlisberger
University of Bern
Switzerland

Tsolmongerel Papilloud
University of Bern
Switzerland

Andreas Zischg
University of Bern
Switzerland

Margreth Keiler
University of Bern
Switzerland

 

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