What is flood risk?
In order to be able to take flood preventive and protective measures, first of all, we have to find out what is the probability for them to occur, where they may appear and how extended they might be, as well as what kind of potential damages they may cause.
By the statistical analysis of floods, supplemented by the analysis of historical hydro- meteorological phenomena, specialists determine the statistical distributions of discharges, including characteristic values relevant for calculations, such as maximum discharges with annual exceedance probabilities of 10%, 5%, 2%, 1%, 0.5%, 0.2% or 0.1% for an examined area. Such probabilities associated with characteristic discharges, as well as the water extent and depth (sometimes also the water velocity, in case the area in question is examined by using 2D modeling), define the flood hazard.
The combination of flood hazard with vulnerability (consequences of the respective floods), respectively potential damages caused to the population, assets or socio-economic objectives, as well as to the environment, results in the flood risk.