Territorial Accessibility and Decision-Making Structure Related to Debris Flow Impacts on Roads in the French Alps

Marina Utasse,Marina Utasse,Marina Utasse,Daniel Brunstein,Daniel Brunstein,Daniel Brunstein,Frederic Leone,Vincent Jomelli,Vincent Jomelli,Vincent Jomelli,Clement Virmoux,Delphine Grancher,Delphine Grancher,Delphine Grancher

doi:10.1007/s13753-016-0088-3

Abstract

The Alps are highly impacted by debris flows that cause major problems for companies and transport networks located in the valley bottoms. One such event occurred in the Rif Blanc catchment and affected the road network in the French Alps, as well as adjacent areas across the Italian border, for several days in June 2012. This article presents two independent approaches to vulnerability assessment. Based on investigations conducted during a survey of local authorities following the event, we compared theoretical risk management and real crisis management in terms of decision making and modes of intervention. Functional vulnerability and territorial consequences were analyzed using a best travel time model of accessibility. We show that a bottom-up approach is practiced in case of actual management planning with a central coordination of general council. Conversely theoretical crisis management shows prefect as the key actor supported by several other state institutions. Our analysis also revealed that a debris flow event with a local impact on the road network has territorial consequences at a regional scale. This study contributes to the discussion about how to minimize the vulnerability of alpine transport networks prone to debris flows. Our results could serve as a decision support tool for public authorities.

Highlights

Debris flows are rapid flows of saturated nonplastic debris within a steep channel (Hungr 2005) that owe their destructive power to the interaction of solid and fluid forces (Iverson 1997)
We focus on a debris flow event that occurred on 4 June 2012 in the Hautes-Alpes district that was viewed as a representative case of debris flows in the French Alps that impact road network (Pavlova et al 2014)
This study tackles the concept of indirect risk by assessing the territorial consequences of the disruption of a road network caused by a debris flow

Summary

Introduction

Debris flows are rapid flows of saturated nonplastic debris within a steep channel (Hungr 2005) that owe their destructive power to the interaction of solid and fluid forces (Iverson 1997). In mountain areas like the Alps, debris flows are a serious threat as they periodically damage critical infrastructure and disrupt transport networks (Jomelli et al 2011; Papathoma-Kohle et al 2011; Fuchs et al 2013). Because many valleys are landlocked, disruption of transport networks affects the damaged area, but extends to all areas and activities linked to it. Many studies on the Alps were focused on understanding the dynamics of debris flows such as the meteorological conditions that were responsible for triggering slope failure (Caine 1980; Guzzetti et al 2007) and links with climate change (Jomelli et al 2007; Pavlova et al 2014). The likelihood that an exposed component would suffer damage as a result of a debris flow is a concept that has not been adequately explored and whose evaluation is not standardized (Gleyze 2007; Fuchs et al 2007)

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