Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 15, 985-995, 2015
https://doi.org/10.5194/nhess-15-985-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 May 2015
Roads at risk: traffic detours from debris flows in southern Norway
N. K. Meyer1,2, W. Schwanghart3, O. Korup3, and F. Nadim1,4 1International Centre for Geohazards (ICG) c/o NGI, Oslo, Norway
2University of Oslo, Department for Geosciences, Oslo, Norway
3University of Potsdam, Institute of Earth and Environmental Science, Potsdam, Germany
4Norwegian Geotechnical Institute (NGI), Oslo, Norway
Abstract. Globalisation and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g. road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load, expressed as vehicle kilometres, because of debris-flow-related road closures. We present two scenarios demonstrating the impact of debris flows on the road network and quantify the associated path-failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and north-western part of the study area are associated with high link-failure risk. Yet options for detours on major routes are manifold and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying on speedy delivery of services and goods.

Citation: Meyer, N. K., Schwanghart, W., Korup, O., and Nadim, F.: Roads at risk: traffic detours from debris flows in southern Norway, Nat. Hazards Earth Syst. Sci., 15, 985-995, https://doi.org/10.5194/nhess-15-985-2015, 2015.
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Short summary
In the past decades the importance of and reliance on all kinds of transport networks has grown extensively making them more vulnerable to any kind of hazard. The linear structure of road networks is especially sensitive to debris flows, a process frequently occurring in the mountainous area of Norway. The paper quantifies the functional risk associated with these processes. The results reveal that the costs related to route closures are strongly related to the information status of drivers.
In the past decades the importance of and reliance on all kinds of transport networks has grown...
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