Time: Monday, June 10, 2013 9:00 am GMT Summer Time (London, GMT+01:00)
Abstract: Taleb (2007) observes that the worst disasters in history have been the unexpected ones because of the inability to brace against them. Such unexpected, large impact events he terms “Black Swan events”, based on the anecdote that, before the discovery of Australia, all swans were considered to be white because of the lack of black swan sightings in the western world. For such Black Swan events prior risk calculations are, invariably, grossly in error.
For many respects, flash floods are the Black Swan events in hydrology. These events often reveal aspects of hydrological behaviour that either were unexpected on the basis of weaker responses or highlight anticipated but previously unobserved behaviour. Characterising the response of a catchment during flash flood events, thus, may provide new and valuable insight into the rate-limiting processes for extreme flood response and their dependency on catchment properties and flood severity. Characterising the human response to flash flood is equally important to improve the societal capability to manage the relevant risks and minimize the impacts.
In the frame of the EU project “HYDRATE”, high-resolution data have been collected and analysed for 25 extreme flash floods across Europe. Most of the selected floods are located in a geographical belt crossing Europe from western Mediterranean (Catalunia and southwestern France) to Black Sea. Criteria for flood selection were high intensity of triggering rainfall and flood response and availability of high-resolution reliable data. Hydrometeorological data collected and collated for each event were checked by using a hydrological model.
I describe results about i) seasonality effects; ii) runoff response dynamics (lag time); iii) rainfall-to-runoff aspects (runoff coefficient and the role of antecedent conditions). I discuss a proposal for the analysis of the human response to flash flood and illustrate the implications for a changing paradigm for flood risk management.
Marco Borga is Associate Professor at the Department of Land, Environment, Agriculture and Forestry of the University of Padova since 7 January 2004. He teaches Hydrology, Hydraulics and Forest Hydrology.His research interests include: Monitoring, analysis, modelling and prediction of hydrological processes over a range of scales from hillslopes to basins; Flood and flash flood hydrology; Integrated hydrological-geomorphic modelling of hillslopes; Forest hydrology; Analysis of hydrological changes; Hydrometeorology and hydrologic analysis by weather radar; Analysis and prediction of natural risks.