A space and time framework for analyzing human anticipation of flash floods

We propose a new simplified vision of flood dynamics through temporal and spatial scales to enhance understanding of potential and limits of human responses to flash floods. Based on data from a set of extreme flash floods that occurred in Europe, we analyze both the runoff response time of flash floods and the asynchronous character of flood peak time generation. We introduce the concept of “timeliness” to quantify the balance in time between the hydrological response of catchments to heavy storms and the human reactions. Timeliness is investigated across the range of spatial scales of concern for flash floods and for various types of anticipation actions. Results are reported for four extreme flash flood events occurred since 2002 in France, Italy and Slovenia. These results indicate that human actions adapt their pace to the physical context and are in a kind of “hurrying” process as the flood danger approaches in time. They show the importance of self-organization and ‘unofficial’ warning in response to flash flooding by individuals and groups. The work draws on flood hazard research findings from hydrology, meteorology and social science and put forward a framework for interdisciplinary collaboration between hydrologists and social scientists.