Roads at risk: traffic detours from debris flows in southern Norway

Abstract

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.

Extending natural hazard impacts: an assessment of landslide disruptions on a national road transportation network

“…Roads classified as tertiary, residential and unclassified (e.g. single lane or residential roads) are omitted and is consistent with similar studies [38,43,[47][48][49]; the omitted minor roads include residential streets, cul-de-sacs and single lane tracks. The network is obtained from OpenStreetMap (OSM), the native format for the simulation software (2.4).…”

“…Here the susceptibility of the road network is classified (see 2.3) using the British Geological Survey GeoSure landslide susceptibility data (e.g. [32,48,51,52]). GeoSure was produced using a combined heuristic and deterministic modelling of environmental and hydrological factors (e.g.…”

“…This is to constrain the scope and complexity of the study (e.g. as in [25,48,49,55]) and to align with national level management of the strategic road network; all other roads are managed at the local authority level.…”

“…This terminology is also applied in past network studies (e.g. [5,38]), however, others also use 'scenario' specifically for potential hazard occurrences restricting 'event' to actual past occurrences [48]. At its most basic, an event set could simply be compilation of the historical occurrences of a hazard, but are commonly supplemented by physical or statistical modelling to extrapolate beyond experience to potential and extremely rare events.…”

Comparing threshold definition techniques for rainfall‐induced landslides: A national assessment using radar rainfall

“…Observational data suggest a positive relationship between rainfall and the occurrence of translational landslides and debris flows, hereafter ‘landslides’ (Iverson, , ; De Vita et al, ; Ballantyne, ). Rainfall‐induced landslides pose a significant threat to life and often result in costly physical damage to property and the disruption of infrastructure, such as transport or power (Jaroszweski et al, ; Meyer et al, ; Postance et al, ). To address these impacts and reduce risk requires an improved understanding of how landslide hazards are distributed in time and what rainfall conditions are relevant to landslide initiation.…”