Flood risk management: Assessment for prevention with hydro-economic approaches

Abstract

A warmer climate, with its increased climate variability, will increase the risk of floods (Parry et al. 2007). Indeed, a warmer climate will increase evaporation and the intensity of water cycling, and a warmer atmosphere can hold more water vapour and has a higher energy poten -tial. As a consequence, rainfall should be more intense, and extreme events should be more frequent (Kundzewick and Schellnhuber 2004). Such changes are not far future projections. Climate modification has already been observed: the frequency of great floods has increased during the twentieth century (Milly et al. 2002).The role of anthropogenic activities on climate perturbation and flood risk modification cannot be ruled out. Pall et al. (2011) revealed that in nine out of ten cases of their climatic simulations, the 20th-century anthropogenic greenhouse gas emissions increased the risk of floods occurring in England and Wales in autumn 2000 by more than 20%, and in two out of three cases by more than 90%. However, the precise magnitude of the anthropogenic contribu -tion to the climatic risk remains uncertain.The role of anthropogenic activities on the economic or socioeconomic risk is much less subject to uncertainties than its role on the climatic risk. Future flood damages depend heavily on the exposure to the flood, i.e. on land-use decisions. Other drivers of the socioeconomic flood risk have non negligible impacts on the damages. Among them are the flood warning and forecast systems, the emergency measures and the longer term precautionary measures and the experience of flood (Thieken et al. 2005). The size of the population located in the floodplain, the value capital accumulated and the value of the services exchanged as well as the sensitiv-ity of these elements are others drivers of the future damages and reveal how vulnerable an economy and a society are to flood.The nature of the flood is also a driver of the damages and of the risk. The intensity of precipitation, the volume and the timing of rainfall, flow velocity and flood duration (Penning- Rowsell et al. 2005) define the nature of the hazard the exposed elements will suffer. For example, during the first decade of the 21st century, the Ebro river basin in Spain experienced