Social and Hydrological Responses to Extreme Precipitations: An Interdisciplinary Strategy for Postflood Investigation

International audienceThis paper describes and illustrates a methodology to conduct postflood investigations based on interdisciplinary collaboration between social and physical scientists. The method, designed to explore the link between crisis behavioral response and hydrometeorological dynamics, aims at understanding the spatial and temporal capacities and constraints on human behaviors in fast-evolving hydrometeorological conditions. It builds on methods coming from both geosciences and transportations studies to complement existing post-flood field investigation methodology used by hydrometeorologists. The authors propose an interview framework, structured around a chronological guideline to allow people who experienced the flood firsthand to tell the stories of the circumstances in which their activities were affected during the flash flood. This paper applies the data collection method to the case of the 15 June 2010 flash flood event that killed 26 people in the Draguignan area (Var, France). As a first step, based on the collected narratives, an abductive approach allowed the identification of the possible factors influencing individual responses to flash floods. As a second step, behavioral responses were classified into categories of activities based on the respondents' narratives. Then, aspatial and temporal analysis of the sequences made of the categories of action to contextualize the set of coping responses with respect to local hydrometeorological conditions is proposed. During this event, the respondents mostly follow the pace of change in their local environmental conditions as the flash flood occurs, official flood anticipation being rather limited and based on a large-scale weather watch. Therefore, contextual factors appear as strongly influencing the individual's ability to cope with the event in such a situation

Comprendre les comportements face à un risque modéré d’inondation. Etude de cas dans le périurbain toulousain (Sud-Ouest de la France)

Les espaces urbanisés soumis à des risques modérés d’inondation pour les vies humaines sont souvent peu considérés dans les études sur la vulnérabilité aux risques naturels en dépit des enjeux qu’ils représentent en termes de gestion de crise. Comment les riverains y font-ils face au danger et quelles sont leurs « bonnes raisons » d’agir? A partir de l’étude socio-géographique de deux inondations récentes (2000 et 2003) dans la périphérie toulousaine (Sud-Ouest de la France), nous montrons que les caractéristiques de l’aléa dans les vallées étudiées influencent les représentations du risque et par conséquent les motivations à se protéger. Face au risque majeur, la vulnérabilité sociale se trouve ainsi augmentée. Pour améliorer la résilience des populations, il convient d’adapter la communication sur les risques: personnaliser l’information, améliorer la compréhension de l’événement vécu et mobiliser de nouvelles formes de médiation entre gestionnaires et riverains

Monolithic metal-containing TiO2 aerogels assembled from crystalline pre-formed nanoparticles as efficient photocatalysts for H2 generation

Nanoparticle-based aerogels are 3-dimensional (3D) assemblies of macroscopic size that maintain the intrinsic properties of the initial nanoparticles. Accordingly, they bear immense potential to become an emerging platform for designing new and efficient photocatalysts. However, to take full advantage of this strategy, understanding of the multiscale processes occurring in such 3D-architectures is essential. Here, we prepared aerogels by co-assembling spherical Au, Pd, and PdAu with TiO2 nanoparticles and investigated their photocatalytic properties for hydrogen generation. During gelation, the anatase nanoparticles undergo oriented attachment, homogeneously entrapping the metal nanoparticles in the growing network. The aerogels offer a high porosity with a mean pore size of ca. 34 nm and a large surface area of about 450 m2 g−1. The porous structure enhances the light-harvesting, reagent transport, and electron migration process, generating 3.5-fold more hydrogen in comparison to the corresponding powders.ISSN:1873-3883ISSN:0926-337