Frédéric Leone

The November, 1st, 1755 Tsunami in Morocco: Can Numerical Modeling Clarify the Uncertainties of Historical Reports?

© 2012 Omira et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The November, 1, 1755 Tsunami in Morocco: Can Numerical Modeling Clarify the Uncertainties of Historical Reports?

Are Debris Floods and Debris Avalanches Responding Univocally to Recent Climatic Change – A Case Study in the French Alps

Debris flow is a dominant mass movement process in mountain areas all over the world and is a significant natural hazard. A classical distinction is made between a debris flood (DF) corresponding to a rapid, surging flow of water, heavily charged with debris in a steep channel, and a debris avalanche (DA) corresponding to a rapid or extremely rapid shallow flow of partially or fully saturated debris on a steep slope without confinement in an established channel (Hungr, 2005). In mountain areas like the Alps, the increase in human activity has resulted in increased risks of natural hazards such as debris flows. There is thus a growing demand for hazard zoning and debris flow protection. However, debris flows are caused by complex interactions between local topography, weather and sediment properties, making the understanding of debris flow activity very difficult. Because anticipated changes in climate may alter the dynamics of slope processes and the frequency or magnitude of extreme events, understanding the mechanisms that link climate and debris flow activity is the first step in any attempt at forecasting. Consequently, many studies have focused on the meteorological conditions that trigger debris flows in different environmental conditions in northern Europe (Innes, 1985; Rapp, 1995; Nyberg and Rapp, 1998) and in the Alps (Haeberli et al., 1990; Zimmerman & Haeberli, 1992; Rebetez et al., 1997). Triggering thresholds based on analyses of intense rainy events or long duration precipitation have been proposed for different spatial scales (Caine 1980; Guzzetti et al., 2008). An increase in temperatures and changes in the amount and frequency of rainfall have been observed in different mountain regions in the last few decades. Such changes in climate conditions could have an impact on the intensity and/or frequency of debris flows. However, only a few authors conducted detailed analyses of the impacts of climate change on DF activity to check the validity of this hypothesis. In British Columbia, Canada, Jakob & Lambert (2009) predicted an increase in the total number of debris flows by the end of the century due to increases in precipitation. From tree-ring series Stoffel & Beniston (2006) clearly show that the debris-flow frequency at Ritigraben (Swiss Alps) increased in the 1866–1895 period that followed the maximum extent of LIA glaciers and that events occurred most often in the early decades of the 20th century.

Analysis of tsunami evacuation maps for a consensual symbolization rules proposal

ABSTRACT Preventing people exposed to natural hazards is a fundamental lever to reduce their vulnerability and the associated risk. In this context, evacuation maps can be considered as a useful tool to educate populations in order to get an appropriate behavior in case of disaster, and to maintain a culture of the risk in exposed areas. Since the catastrophic events in the Indian Ocean and Japan, local initiatives for the creation of tsunami evacuation maps have developed worldwide. However, no clear recommendations for the elaboration of these maps have already been proposed. This lack concerns the methods and rules used to create and represent the information present in the map. So, this article seeks to provide consensual symbolization rules for tsunami evacuation maps. To achieve this objective, a critical analysis was conducted from a sample of 30 tsunami evacuation maps. As a result, major trends and recurring choices have been extracted and compiled in a proposition for symbolization rules. This proposition, which has been implemented on various sites in the Mediterranean and Caribbean seas, can be seen as a first contribution for the harmonization of tsunami evacuation maps, in order to provide a universal cartographic language for exposed populations.

14 – Assessing Vulnerability to Flooding: Progress and Limitations

Abstract: The geographical approach to risks has evolved over the last few decades. A “hazard-centered” process has given way to a more integrated approach, which takes in the social and territorial aspects of vulnerability. Vulnerability has conventionally been considered a component of risk but the scientific community still perceived it as only a minor part of the definition. However, the concept of vulnerability has evolved, become clearer and stabilized; more diagnostic methods have been developed on various scales. The limitations are due to the negative connotations of vulnerability, which often discourages risk managers (particularly elected representatives) from using it, and to the existence of a sort of “glass ceiling” that makes it impossible to entirely model vulnerability, fostering an image of methodological shortcomings compared with the “hard” sciences that govern risk assessment. Finally, the main challenge is still to use diagnostic methods to actually reduce risk.

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

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.