Local stakeholders' perception of muddy flood risk and implications for management approaches : a case study in Alsace (France)

The inventory of muddy floods in France indicates that the occurrence of these events seriously increased in the North West and the East of the country. Muddy floods triggering can largely be explained by physical characteristics such as a hilly topography, soils prone to crust, and/or heavy rainfall in spring. Although the physical processes are well known by now and despite increasing information about the need of mitigation measures, no significant reduction of these disasters has been registered. Therefore, this should be explained by factors others than scientific reasons or technical knowledge acquisition difficulties. This paper deals with a study of muddy flood risk in five municipalities belonging to three catchments (Alsace—NE France). These catchments have been suffering from several muddy flood events in the past 20 years, and, despite the implementation of mitigation measures, no decrease of their frequency has occurred. This study focuses on risk perception: we assume that obtaining information on risk perception contributes to the understanding of the main social factors that should be taken into account in an efficient muddy flood risk management policy. To gather data, we used surveys based on individuals' interviews and questionnaires, focusing on the local stakeholders in charge of the risk management. A sampling strategy based on a spatial distinction of runoff areas was used to select the areas to be surveyed. The surveys results highlight significant differences in perception between respondents. These differences depend in particular on their location within the catchment (i.e. erosion or sedimentation area). Moreover, almost the half of the respondents trusts in information provided by the local authorities. Our results provide some insights about the type and the source of information related to risk mitigation that should be considered when implementing an efficient regulation policy.