Social and hydrological responses to extreme precipitations: An interdisciplinary strategy for post-flood investigation

This paper describes and illustrates a methodology to conduct post-flood investigations based on interdisciplinary collaboration between social and physical scientists. The method, designed to explore the link between crisis behavioral response and hydro-meteorological dynamics, aims at understanding the spatial and temporal capacities and constraints on human behaviors in fast evolving hydro-meteorological conditions. It builds on methods coming from both geosciences and transportations studies to complement existing post-flood field investigation methodology used by hydro-meteorologists. We propose an interview framework, structured around a chronological guideline to allow people who experienced the flood first hand to tell the stories of the circumstances in which their activities were affected during the flash flood.This paper applies our data collection method to the case of the June 15th 2010 flash flood event that killed 26 persons in the Draguignan area (Var, France). As a first step, based on the collected narratives, an abductive approach allowed us to identify the possible factors influencing individual responses to flash floods. As a second step, behavioral responses were classified into categories of activities based on the respondent's narratives. Then, we propose a spatial and temporal analysis of the sequences made of the categories of action to contextualize the set of coping responses with respect to local hydro-meteorological conditions. 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.