De la vulnérabilité de la parcelle à celle de l'exploitation agricole : un changement d'échelle nécessaire pour l'évaluation économique des projets de gestion des inondations

[Departement_IRSTEA]Eaux [TR1_IRSTEA]GEUSIEn France, peu de travaux ont été consacrés à la caractérisation de la vulnérabilité des zones agricoles exposées aux inondations, encore moins à son utilisation dans le cadre d'une évaluation économique de politique de gestion des inondations. Nous proposons dans cet article un modèle conceptuel de la vulnérabilité agricole pouvant servir à une telle évaluation, lorsque les politiques visent à une modification de l'événement physique à l'origine de l'inondation ou à une modification de la vulnérabilité des enjeux exposés à cet événement. / Flood management policies promoted by French government impact agriculture land in two ways. Firstly, they may be designated as potential areas for flood expansion. Secondly, since the 2003 law, local authorities have the right to flood these areas more than those which have been deemed to be more vulnerable (urban areas). Meanwhile, policy-driven appraisals of flood management projects are becoming commonplace in France. This highlights the need to better understand agricultural vulnerability and to develop methods for quantifying it. To introduce our approach, we first present the research conducted by Plan Loire which marks a shift away from existing practices of agriculture vulnerability assessment by considering vulnerability at the farm scale rather than at the plot scale. Based on ex-post flood damage assessment and the results of stakeholders questionnaires in the agricultural sector, forty seven determinants of farm vulnerability to flooding were identified and classified. These determinants were used to draft a guide for farmers. This guide aims to highlight the impacts their farm activities could face in case of flooding and to identify measures to mitigate their vulnerability. At the present, this guide is used along the Rhone River and will be probably used along the Loire River in the future. The current application of these guides to mitigate vulnerability of farms revealed the need for further research which is partly presented here. By focusing on the farming system, we aimed at providing a framework to economically assess agricultural vulnerability to flooding. Firstly, we identified flood effects at the farming system scale including possible interactions with the territorial scale, in order to propose a conceptual model which provides a framework for economic assessment. Finally, we discuss the implications for projects economic appraisal. The provided framework for agricultural vulnerability assessment would enable a selection of most efficient measures to mitigate farm vulnerability using a ratio depending on the agricultural context. It would also help to prioritize projects to reduce vulnerability by economic appraisal at a wider spatial scale such as water basin